Processing method for etching a substrate

ABSTRACT

A processing method for etching a substrate is described. This method includes subjecting a surface of a substrate to be processed to selective irradiation with a light in a gas atmosphere to form a surface-modified layer. The substrate surface with the surface-modified layer is then annealed to stabilize and make the surface-modified layer more etch resistant. Both the stabilized surface-modified layer and a non-modified portion of the substrate are then subjected to dry etching, thereby utilizing the higher resistance to dry etching of the stabilized surface-modified layer compared to the non-modified portion to selectively etch the non-modified portion to a desired depth.

This application is a division of application Ser. No. 08/251,666 filedMay 31, 1994, pending, which is a continuation of Ser. No. 07/764,939filed Sep. 24, 1991, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a processing method and an apparatususable for the method. More particularly it relates to a processingmethod that can apply the desired patterning to semiconductors, metals,insulators, etc., and an apparatus that can be used for such patterning.

2. Related Background Art

One of the important techniques in the fabrication of semiconductordevices is photolithography. In the photolithography, a complicated andcumbersome process comprising the steps of resist coating, patternexposure, development, etching, resist removing, etc. has been in wideuse.

In recent years, as typified by semiconductor memory devices, there israpid progress in providing devices with a larger capacity and theirfunctions with a higher performance. With such progress, circuitpatterns are being made finer and the structure of circuits is becomingmore complicated. As for display devices such as liquid-crystal displaydevices and plasma-display devices, they are being made larger in sizeand device functions thereof are being made more complicated.Fabrication of these devices by the use of the above processes mayresult in an increase in cost because of the processes that may be morecomplicated, and may bring about a decrease in yield because of anincrease in generation of dust, thinly causing an increase in cost as awhole.

Thin-film devices are mainly fabricated by a process comprising thesteps of forming on a substrate a thin film of a metal, a semiconductor,an insulator or the like, and finely processing the thin film to havethe desired pattern. In recent years, as typified by semiconductormemory devices, there is rapid progress in providing devices with largercapacity and their functions with a higher performance. With suchprogress, circuit patterns are being made finer and the structure ofcircuits is becoming more complicated. As for display devices such asliquid-crystal display devices and plasma-display devices, they arebeing made larger in size and device functions thereof are being mademore complicated. For this reason, film formation and also etching forapplying fine processing, which had been carried out by a process makinguse of a solution, are now mainly carried out by what is called a dryprocess making use of plasma or excited gas in vacuum or inpressure-reduced gas. The photolithography commonly used for applyingthe desired fine processing, however, requires a complicated andcumbersome process comprising the steps of resist coating, patternexposure, development, etching, resist removing, etc. Of these steps,the steps of resist coating, development and resist removing make use ofsolutions, and hence it is impossible for all the steps to be carriedthrough a dry process. Accompanying these steps, the photolithographyalso requires a cleaning step or a drying step after the step ofsolution treatment, resulting in an increase in steps and making theprocess more complicated. The resist used in the above photolithography,when stripped, may become a source of dust, thus causing a decrease inyield and an increase in cost.

As a method of carrying out fine processing without use of such aresist, there is a method of carrying out fine processing by a processcomprising the steps of selectively irradiating the surface of a film tobe processed, with light in a modifying gas to form a surface-modifiedlayer having thereon a pattern structure, and dry-etching asurface-unmodified layer, using the surface-modified layer as aprotective film. This process makes it possible to carry out fineprocessing wherein all the steps are carried out through a dry process,without use of photolithography, and hence to promise a low cost and ahigh yield.

On the other hand, in place of the above photolithography making use ofa resist, a photoetching technique is proposed which can form a patternby a process wherein the complicated process has been greatlysimplified, as disclosed in Sekine, Okano and Horiike, Draft Collectionsof Lectures in the 5th Dry Processing Symposium, page 97 (1983). Thispaper reports a process in which a substrate comprising a polysilicon(poly-Si) deposited thereon is placed in a reaction chamber into whichchlorine gas has been introduced and the Si substrate is selectivelyirradiated with ultraviolet light through a mask, whereupon only thepart irradiated with the ultraviolet light is etched and a pattern isformed on the poly-Si film. Use of this process makes it possible toomit the steps of resist coating, development and resist removing, tosimplify the process, to improve the yield and to greatly reduce thecost. Use thereof also may cause no damage due to ion irradiation, whichhas been questioned in conventional reactive ion etching, and henceenables damage-free etching.

In this photoetching process, however, it is very difficult to performfine processing faithful to a pattern because of the scattering ordiffraction of light at the inside of processed grooves. In addition, inorder to carry out perfect anisotropic etching, a side-wall protectivefilm must be formed, and as a result this film may remain as a residueto have an ill influence on the device. In instances in which large-areadisplay devices as exemplified by 14 inch liquid-crystal display devicesare manufactured, the poly-Si is etched at a very low rate, which is 40Å/min at most, as reported in the above Sekine et al.'s report. This islower by the factor of about 2 figures than those in other etchingprocesses. Moreover, under existing circumstances, the process can notreach the level of practical use at all even if an excimer laser havingan output which is highest at present (about 100 W) is used as a lightsource, since the irradiation area is larger by the factor of ˜2×10⁴times than the conventional one. In addition, there has been the problemthat a substance produced as a result of etching reaction may bedeposited on the window through which the ultraviolet light is shed andhence the window must be cleaned often.

As stated above, a process has been proposed which is a method ofcarrying out fine processing by a process comprising the steps ofselectively irradiating the surface of a film to be processed, withlight in a modified gas to form a surface-modified layer having thereona pattern structure, and dry-etching a surface-unmodified layer, usingthe surface-modified layer as a protective film (an etching mask). Thisprocess makes it possible to carry out fine processing without use ofphotolithography, and hence achieve an improvement in yield at a lowcost. The process, however, often requires a long period of time or astrong light power at the time of the surface modification. If theprocessing is carried out for a short time or at a weak light power, theprotective film formed by the surface modification can not be chemicallystrongly bonded or may be formed in an insufficient thickness, oftenbringing about an insufficient resistance of the protective film to giveno desired etching depth.

Also when a film is selectively deposited on the surface-modified layeror the surface-unmodified layer by utilizing a difference in propertiessuch as electron donative properties between the surface-modified layerformed by surface modification by the above selective light irradiationand the surface-unmodified layer, the difference in properties such aselectron donative properties can not be sufficient if the protectivelayer formed by the surface modification is not chemically stronglybonded or formed in an insufficient thickness, so that no satisfactoryselectivity may be obtained in the subsequent deposition.

In the method described above, aluminum is mainly used as a material forthe electrodes or wiring of devices, where these electrodes and wiringhave been conventionally formed by a method in which an aluminum film isdeposited on the whole surface of a substrate and then etching iscarried out to form the desired pattern. As a method of depositing thealuminum film, sputtering such as magnetron sputtering has been used.Since, however, the sputtering is commonly a physical deposition processwhich is based on the flying in vacuum, of particles sputtered from atarget, the film may be formed having extremely small thickness at stepportions or on insulating film side walls, resulting in a disconnectionin an extreme instance. Non-uniformity in layer thickness ordisconnection may cause the problem that the reliability of LSI isseriously lowered.

In order to solve the problems as discussed above, various types of CVD(chemical vapor deposition) processes are proposed. In such processes, achemical reaction of a starting material gas is utilized in any form inthe course of film formation. In the case of plasma CVD or photo-inducedCVD, the starting material gas is decomposed in a gaseous phase, and anactive species produced there further reacts on the substrate to causefilm formation.

Since in these CVD processes the reaction takes place in a gaseousphase, the surface can be well covered irrespective of any surfaceirregularities on the substrate, but the carbon atoms contained in thestarting gas molecules may be undesirably incorporated into the film. Inparticular, in the case of plasma CVD, there has been the problem thatcharged particles cause damage, what is called plasma damage, as is thecase of sputtering.

In heat CVD, the reaction taking place mainly on the substrate surfacecauses a film to grow, and hence the surface can be well coveredirrespective of any surface irregularities on the substrate. This canprevent disconnection at step portions or the like. This process is alsofree from the damage caused by charged particles that may be caused inplasma CVD or sputtering. Hence, the heat CVD has been studied fromvarious approaches as a method of forming aluminum films. As a method offorming an aluminum film by commonly available heat CVD, a method isused in which an organic aluminum having been dispersed in a carrier gasis transported onto a heated substrate and gas molecules are thermallydecomposed on the substrate to form a film. In an example disclosed, forexample, in Journal of Electrochemical Society, Vol. 131, page 2175(1984), triisobutyl aluminum [(i-C₄ H₉)₃ Al] (hereinafter "TIBA") isused as the organic aluminum and film formation is carried out at atemperature of 260° C. under a reaction tube pressure of 0.5 Torr toform a film of 3.4 μΩ·cm.

When the TIBA is used, no continuous film can be obtained unless apretreatment is applied such that TiCl₄ is flowed before the filmformation to activate the substrate surface so that nuclei can beformed. Including the instance where TiCl₄ is used, there is commonly adisadvantage that use of the TIBA may bring about a poor surfaceflatness. Japanese Patent Application Laid-open No. 63-33569 discloses amethod in which no TiCl₄ is used and instead an organic aluminum isheated in the vicinity of a substrate to thereby form a film. In thisinstance, as clearly stated in the publication, it is necessary toprovide a step of removing an oxide film naturally formed on thesubstrate surface. The publication also discloses that since the TIBAcan be used alone, it is unnecessary to use a carrier gas other thanTIBA but Ar gas may be used as the carrier gas. There, however, is noassumption as to the reaction of TIBA with another gas (e.g., H₂) andthere is no disclosure as to the use of hydrogen as the carrier gas. Thepublication also mentions trimethyl aluminum (TMA) besides TIBA, but hasno specific disclosure as to the gases other than them. This is due tothe fact that any use of any organic metals must be individually studiedsince, in general, chemical properties of organic metals greatly changedepending on slight changes in organic substituents attached to metalelements.

Electrochemical Society, Draft Collections for the 2nd Symposium,Japanese Branch, page 75 (Jul. 7, 1989) discloses a method concerningthe formation of aluminum films by double-wall CVD method. In thismethod, an apparatus is so designed that the gas temperature becomeshigher than the substrate temperature by the use of TIBA. This methodhas the disadvantages not only that it is difficult to control thedifference between the gas temperature and the temperature on thesubstrate surface but also that bombs and conveying pipes must beheated. This method also has the problems such that no uniformcontinuous film can be obtained unless the film is made thick to acertain extent, the film has a poor flatness and the selectivity can notbe maintained for a long period of time.

Etching of aluminum may bring about after-corrosion, i.e., the corrosionof aluminum that may be caused by HCl generated because of the use of achlorine gas such as Cl₂ or CCl₄ as a result of reaction of Cl₂ or itsreaction product such as AlCl₃ adhered during etching, with waterremaining in the air or etching chamber. This corrosion is a great causeof the disconnection of wiring or electrodes.

Meanwhile, besides these techniques, there is a method making use ofphoto-induced CVD, in which the surface of a substrate is selectivelyirradiated with light-to cause photochemical reaction only on theirradiated surface so that a material can be selectively depositedthereon. Since, however, it is impossible to cause no reaction at all inthe gaseous phase, the material may necessarily be deposited on the partother than the irradiated part. In addition, the photo-induced CVDcommonly brings about slow deposition, where the rate of deposition issmaller by the factor of one figure than that of the heat CVD.

As semiconductor devices are made more highly integrated and made tohave a higher performance, attention is also drawn to CVD, etching,surface modification, cleaning, etc. which utilize light irradiation.This is because such a process enables low-temperature processing andcauses less damage, as is characteristic of a photo-process, and alsobecause spatially selective processing has become indispensable for theprocess of fabricating semiconductor devices. Incidentally, a commonprocess making use of photo-processing includes;

1) a process in which the surface of a substrate is irradiated withlight in a reactive gas atmosphere to cause excitation and decompositionof the reactive gas to bring several kinds of gases into reaction (i.e.,gaseous phase reaction), whereby a deposit is formed on the surface orthe surface is etched or cleaned; and

2) a process in which the surface of a substrate is heated by lightirradiation to cause the surface to thermochemically react with areactive gas or irradiated with light to cause the surface tophotochemically react with a reactive gas (i.e., interface reaction),whereby a deposit is formed on the surface or the surface is etched orcleaned.

The former process can be exemplified by a process in which the surfaceof a substrate is irradiated with a KrF excimer laser light in a gasatmosphere comprising SiH₄ and O₂, to cause SiH₄ and O₂ to react in thegaseous phase so that SiO₂ is deposited on the substrate. In thismethod, however, the reaction product may scatter at random in thegaseous phase and hence there is basically no spatial selectivity. Asfor the latter process, it can be exemplified by a process in which thesubstrate is etched in a Cl₂ gas atmosphere. Although no details of thereaction process have been elucidated in this method, it is presumedthat the electrons excited on the surface irradiated with light arereceived by the chlorine atoms and incorporated into the Si substrate,in the state of which the reaction proceeds, and hence it is possible tocause the reaction only on the surface irradiated with light andtherefor to effect spatially selective processing.

Of the above conventional thin-film device processing methods describedabove, the methods making use of photolithography have the problems of adecrease in yield and an increase in cost. The method making use of thephotoetching technique has the problem that it is impossible to performfine processing faithful to a pattern because of the scattering ordiffraction of light at the inside of processed grooves. In addition, inorder to carry out perfect anisotropic etching, a side-wall protectivefilm must be formed, and this film may remain as a residue to have a badinfluence on the device. Moreover, the poly-Si is etched at a rate aslow as about 40 Å/min, which is lower by the factor of 2 figures thanthose in other etching processes. In instances in which large-areadisplay devices as exemplified by 14 inch liquid crystal display devicesare manufactured, the irradiation area becomes larger by the factor of˜2×10⁴ times than the experimental data, and hence the process can notreach the level of practical use at all even if an excimer laser with anoutput which is highest at present (about 100 W) is used as a lightsource. In addition, there has been the problem that, where theultraviolet light having passed the mask is shed on the Si substratethrough an ultraviolet irradiation window provided in the wall of thereaction chamber, a substance produced as a result of etching reactionmay be deposited on this ultraviolet irradiation window and may absorbthe ultraviolet light to cause a lowering of etching speed, and hencethe ultraviolet irradiation window must be cleaned often withdifficulty.

Of the above fine-processing methods used in thin-film devices, themethod making use of photolithography requires use of a resist, which isstripped, and hence the method has been involved in the problem that theresist stripped comes out as dust and adheres to the surface of asubstrate to cause a deterioration of the performance of devices andalso to bring about a decrease in yield.

In the method in which the dry etching is carried out without use of thephotolithography, manufacture at a low cost and in a high yield can beachieved, but no sufficiently high etching selectivity can be attainedbetween the protective film serving as a mask in etching and the film towhich the fine processing is to be applied. Thus there is the problemthat if the protective film formed by surface modification carried outonce has a small thickness, the protective film serving as a mask in dryetching may disappear and hence the etching of the film to which thefine processing is to be applied can not be in a sufficient amount (ordepth).

As another problem, these photo-excitation processes discussed aboveleave some room for improvement for their better adaptation tosemiconductor devices having been made more highly integrated and madeto have a higher performance. One of the room of improvement is that alight-absorptive cross-sectional area or a light-reactivecross-sectional area is so small that the rate of processing is low. Forexample, in the photo-excitation etching of a silicon substrate, mostpapers report that the etching rate is approximately 100 to 2,000 Å/min(Research Reports XII on New Electronic Materials, Photo-excitationProcessing Technique Research Report 1, Japan Electronic IndustryAssociation, March 1986), which is an etching rate lower by the factorof about one figure than that in the conventional plasma etching. Ininfrared irradiation using a CO₂ laser or the like, the thermochemicalreaction caused by the heating of the substrate is mainly utilized, andhence images may be blurred because of the diffusion of heat. This hassometimes caused a problem when the substrate surface must be processedin a good selectivity.

In the above photoetching, it is impossible to perform fine processingfaithful to a pattern because of the scattering or diffraction of lightat the inside of processed grooves. In addition, in order to carry outperfect anisotropic etching, a side-wall protective film must be formed,and this film may remain as a residue to have an ill influence on thedevice.

In instances in which large-area display devices as exemplified by 14inch liquid-crystal display devices are manufactured, the poly-Si isetched at a very low rate, which is 40 Å/min at most, as reported in theSekine et al.'s report. This is lower by the factor of about 2 figuresthan those in other etching processes. The process can not reach thelevel of practical use at all even if an excimer laser having anirradiation area which is larger by the factor of at least 2×10⁴ timesand having an output which is highest at present (about 100 W) is usedas a light source. In addition, there has been the problem that asubstance produced as a result of etching reaction may be deposited onthe ultraviolet irradiation window through which the ultraviolet lightis passed, to cause a lowering of the etching rate, and hence the windowmust be cleaned often.

SUMMARY OF THE INVENTION

The present invention was made taking account of the above problemsinvolved in the prior art. An object of the present invention is tomaterialize a processing method that can rapidly apply fine processingfaithful to a pattern, and can improve the yield, and an apparatus thatcan be used for such a method.

Another object of the present invention is to materialize a processingmethod that can form in a sufficiently large thickness the protectivefilm serving as a mask in dry etching and thereby can give a sufficientamount of etching.

Still another object of the present invention is to provide a method of,and an apparatus for, applying fine processing to semiconductor devices,that can accurately form a circuit pattern by the use of a simpleprocess.

A further object of the present invention is to solve the problems thatwhen the devices are fabricated by photolithography, not only theprocess is complicated resulting in an increase in cost but also dust isgenerated or increased to bring about a decrease in yield and to causean overall increase in cost.

A still further object of the present invention is to propose a methodcapable of forming a protective film that can give a chemically wellstrong bond and have particles with a large diameter so as to have astrong etching resistance.

A still further object of the present invention is to provide aphoto-processing method that enables high-rate processing, and aprocessing apparatus to which such a processing method can be applied.

A still further object of the present invention is to provide aphoto-processing method that can process in an excellent selectivity thedesired region on the substrate, and a processing apparatus to whichsuch a processing method can be applied.

A still further object is to provide a semiconductor fabrication method,and a semiconductor fabrication apparatus, that can form an electrode orwiring in a high selectivity and in a good yield, by the use of aluminumwhich is a good conductor or a metal mainly composed of aluminum,without use of any resist.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1D stepwise illustrate a procedure for pattern formationaccording to Example 1 of the present invention.

FIG. 2 cross-sectionally illustrates the constitution of an apparatusfor fabricating a device according to the procedure shown in FIGS. 1A to1D.

FIGS. 3 and 4 cross-sectionally illustrate the constitution of otherexamples of a surface-modified layer forming chamber 112a and an etchingchamber 112c, respectively, shown in FIG. 2.

FIGS. 5A to 5D stepwise illustrate cross-sectionally a procedure forfabricating a device according to Example 3 of the present invention.

FIGS. 6 to 10 cross-sectionally illustrate the constitution of acleaning chamber 201, a sputtering film forming chamber 202, a plasmafilm forming chamber 203, an etching chamber 204 and a latent imageforming chamber 205, respectively, that are used in carrying out thepresent invention.

FIGS. 11A to 11D stepwise illustrate cross-sectionally a procedure forfabricating a device according to Example 4 of the present invention.

FIGS. 12A to 12F stepwise illustrate cross-sectionally a procedure forfabricating a device according to Example 5 of the present invention.

FIGS. 13A to 13G are diagrammatic cross sections to illustrate afine-processing method of the present invention.

FIGS. 14A to 14F are diagrammatic cross sections to illustrate afine-processing method of the present invention.

FIGS. 15A to 15D and 16A to 16H each diagrammatically illustrate surfacephoto-processing steps.

FIGS. 17A to 17C, 21A to 21C and 23A to 23C each diagrammaticallyillustrate a typical example of a surface photo-processing method of thepresent invention.

FIGS. 18, 22 and 24 each diagrammatically illustrate a typical exampleof a surface photo-processing apparatus of the present invention.

FIG. 19 is a graphic representation to show the relationship betweensubstrate temperature and dead-time at the time of the formation of asurface-modified layer.

FIG. 20 is a graphic representation to show the relationship betweensubstrate temperature and chemical shift at the time of the formation ofa surface-modified layer.

FIG. 25 diagrammatically illustrates a CVD apparatus used forselectively depositing aluminum.

FIG. 26 diagrammatically illustrate an example of a photo-processingapparatus that can preferably carry out the photo-processing accordingto the present invention.

FIG. 27 diagrammatically illustrates another example of the apparatusshown in FIG. 26.

FIG. 28 diagrammatically illustrates still another example of theapparatus shown in FIG. 26.

FIG. 29 diagrammatically illustrates a preferred example of afine-processing apparatus according to the present invention.

FIG. 30 diagrammatically illustrates an example of a microwave plasmaetching apparatus.

FIG. 31 diagrammatically illustrates the constitution of an apparatusfor fabricating a semiconductor device according to the presentinvention.

FIG. 32 diagrammatically illustrates the constitution of the main partof a fabrication apparatus wherein the present invention is applied to avacuum through-process.

FIGS. 33A to 33E are a schematic process chart to show a procedure forthe fabrication of an amorphous silicon photosensor fabricated using themethod of the present invention.

FIG. 34 cross-sectionally illustrates an example of an apparatus for thefine processing of a semiconductor device, according to the presentinvention.

FIG. 35 cross-sectionally illustrates another example of the cleaningchamber.

FIG. 36 cross-sectionally illustrates another example of the etchingchamber.

FIG. 37 cross-sectionally illustrates another example of the latentimage forming chamber.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A first embodiment of the processing method of the present inventionthat can achieve the above objects comprises;

a first step of depositing on a substrate which is a specimen a film ofany one of a semiconductor, a metal and an insulator;

a second step of subjecting the surface of the film deposited in thefirst step, to irradiation with a beam having a given energy to producea physical damage on the surface;

a third step of subjecting the film surface on which the physical damageis produced in the second step, to selective irradiation with light topartially cause a photochemical reaction so that a mask patterndepending on the desired device structure is formed on the film surface;and

a fourth step of carrying out photoetching using as a shielding memberthe mask pattern formed in the third step.

The apparatus used for the above method comprises;

a latent image forming chamber in which a specimen is selectivelyirradiated with light;

a modified layer forming chamber in which said specimen is irradiatedwith a beam having a given energy; and

a photoetching chamber in which photoetching is carried out;

said modified layer forming the photoetching chamber and saidphotoetching chamber being connected with said latent image formingchamber through a gate valve.

According to this method, the beam irradiation in the second stepproduces a physical damage such as disconnection of bonds or generationof traps at the part extending from the surface of the deposited film toa given depth thereof. In the third step subsequently carried out, amask pattern is formed utilizing photochemical reaction caused by theselective irradiation with light. Since the damage as described abovehas been formed in the surface of the film, the photochemical reactionis accelerated to give a uniform photochemical reaction. Hence, thedevice structure formed as the mask pattern can be made dense and theetching inhibitory power can be improved, so that the photoetchingcarried out in the fourth step can achieve a good fine-processingperformance.

In the apparatus in which the modified layer forming chamber and thephotoetching chamber are each connected with the latent image formingchamber through a gate valve, the specimen can be moved between therespective chambers without exposure of the specimen surface to theatmosphere, and hence it becomes possible to prevent deterioration ofdevices and adhesion of dust.

Another embodiment of the processing method of the present inventionthat can achieve the above objects comprises;

a first step of depositing on a substrate a film to be etched;

a second step of subjecting the film to be etched, to selectiveirradiation with light to form a protective film having a partiallymodified surface; and

a third step of subjecting said film to be etched, to dry etching usingsaid protective film as an etching mask;

wherein said first step and said second step are continuously carriedout plural times to respectively deposit on said substrate said film tobe etched and said protective film in plurality, and thereafter saidthird step is carried out.

According to this method, the protective film serving as an etching maskin dry etching is formed in plurality. The etching depth obtained by theetching corresponds to the total layer thickness of all the protectivefilms, and hence controlling the number of the protective film to beformed enables control of the etching depth when the fine processing isapplied.

Still another embodiment of the processing method of the presentinvention that can achieve the above objects comprises the steps of;

subjecting a surface to be processed, to selective irradiation withlight in the desired gas atmosphere to form a surface-modified layer inthe desired region; and

subjecting said surface to be processed, to dry etching using saidsurface-modified layer as an etching mask;

wherein said surface-modified layer is annealed before the step of saidetching.

According to this method, a substrate surface to be processed isselectively irradiated with light in the desired gas atmosphere to forma surface-modified layer having the desired pattern on the surface to beprocessed, and then the surface to be processed on which nosurface-modified layer is formed is dry-etched using thesurface-modified layer as a protective film (a resist). This makes itpossible to carry out fine processing without use of photolithographyand to promise a high yield at a low cost.

In some instances, the etching selectivity of the surface (film) towhich the fine processing should be applied is not sufficiently highwith respect to the protective film serving as a mask in etching or aprotective film formed by surface modification is not chemicallystrongly bonded or comprises particles with a small diameter where thefine processing should be applied in a greater depth. In such instances,resistance to etching may become short to make the protective film havean insufficient resistance. The present invention, however, proposes aprocessing method in which the protective film chemically stronglybonded, having particles with a large diameter, being stable and firmand having a high etching resistance is formed so that the aboverequirements can be well satisfied.

In other words, the present invention gives a protective film with ahigh etching resistance, formed by subjecting a surface-modified layerformed in the desired gas atmosphere to irradiation with electromagneticwaves such as laser beams, electron beams and light or by heating asurface-modified layer, or by carrying out both in combination, so thatnot only the problems hitherto involved can be eliminated but also theabove requirements can be satisfied.

As described above, the annealing of the surface-modified layer servingas a protective film (a mask) in etching makes it possible to form aprotective film of a high etching resistance chemically strongly bondedbecause of increased particle diameter accelerated crystallization, ordecrease of dangling bonds or bonding with impurities to approach thestoichiometric ratios in the solid phase of the surface-modified layer.As a result, it becomes possible to obtain the desired amount (depth) ofetching of the film to which the fine processing should be applied.

As a result of intensive studies made taking account of the problemsinvolved in the prior art as previously discussed, the processing methodof the present invention can form a protective film with a chemicallywell strong bond, with a well large thickness and with a high etchingresistance, compared with the prior art. An embodiment of such aprocessing method of the present invention that can achieve the aboveobjects comprises the steps of;

subjecting a surface to be processed, to selective irradiation withlight in the desired gas atmosphere to form a surface-modified layer inthe desired region; and

applying selective processing to said surface-modified layer or thesurface-unmodified layer;

wherein said surface to be processed is heated in the step of formingsaid surface-modified layer.

The processing apparatus that can achieve the above objects comprises areaction vessel, gas feeding means for feeding a reactive gas into saidreaction vessel, and light guiding means for guiding processing lightinto said reaction vessel, a substrate placed in said reaction vesselbeing irradiated with said processing light so that the surface to beprocessed is processed;

wherein said apparatus is provided with means for selectively heatingsaid surface to be processed.

According to this method, the heating of the film to which surfacemodification is applied, in the step of forming the surface-modifiedlayer, accelerates photochemical reaction on the surface irradiated withlight, and hence the surface-modified layer can have a chemicallystronger bond and also have a greater thickness. This can achieve i) animprovement in etching resistance of the surface-modified layer and ii)an increase in difference in electron donative properties between thesurface-modified layer and the unmodified layer. The surface-modifiedlayer having been formed may be further heated, whereby thesurface-modified layer can be converted to a region with a stableresistance. This enables pattern formation with ease.

The processing method that can achieve the above objects may alsocomprise the steps of;

introducing into a reaction vessel a reactive gas and a processing lightthat brings the reactive gas into excitation; and

processing with the excited reactive gas the surface of a substrateplaced in said reaction vessel;

wherein said surface of the substrate is simultaneously irradiated withlight generated by a first light-generation means that causes vibrationof the molecules constituting said surface of the substrate and lightgenerated by a second light-generation means that causes photochemicalreaction of said reactive gas with said surface of the substrate, toprocess said substrate.

The processing apparatus that can achieve the above objects may alsocomprise a reaction vessel, a gas feeding means for feeding a reactivegas into said reaction vessel, and a light guiding means for guidingprocessing light into said reaction vessel, said reactive gas beingbrought into excitation with said processing light to process thesurface of a substrate placed in said reaction vessel;

wherein said apparatus comprises;

a first light-generating means for generating light that excitesvibration of the molecules constituting said surface of the substrate;

a second light-generating means for generating light that causesphotochemical reaction of said reactive gas with said surface of thesubstrate; and an irradiating means that simultaneously irradiates saidsurface of the substrate with the light generated by said firstlight-generating means and the light generated by said secondlight-generating means.

According to the above method, the simultaneous irradiation on thesubstrate with the light that excites vibration of the moleculesconstituting said surface of the substrate and the light that causes thephotochemical reaction accelerates the reaction of the surface with thereactive gas. This makes it possible to process the substrate at a highrate. Since the photochemical reaction can be made to selectively takeplace on the surface irradiated with the processing light, it is alsopossible to carry out the desired processing in a good selectivity.

Still another embodiment of the processing method of the presentinvention that can achieve the above objects comprises the steps of;

subjecting in a modifying gas atmosphere the surface of a substrate toselective irradiation with light that has an energy greater than abinding energy of a compound constituting said surface of the substrateand is capable of reducing said compound, to form on said surface of thesubstrate a surface-modified layer having a pattern structureconstituted of a reduced product; and

etching the surface-unmodified layer using said surface-modified layeras a protective film.

The apparatus that can achieve the above objects may also comprise;

a surface photo-processing zone comprising a first reaction vessel, alight guiding means for guiding processing light into said firstreaction vessel and an evacuating means for evacuating the inside ofsaid first reaction vessel, wherein the surface of a substrate placed insaid first reaction vessel is irradiated with said processing light toform thereon a surface-modified layer; and

an etching zone comprising a second reaction vessel, a reactive gasfeeding means for feeding a reactive gas into said second reactionvessel and an energy supplying means for supplying an energy forgenerating plasma in said second reaction vessel, wherein thesurface-unmodified layer is etched using said surface-modified layer asa mask,

said processing light having an energy greater than a binding energy ofa compound constituting said surface of the substrate and capable ofreducing said compound.

According to the above method, the compound constituting the surface ofthe substrate is selectively reduced to form the surface-modified layer,and the surface-unmodified layer is etched using the surface-modifiedlayer as a protective film. Hence it becomes possible to carry outhigh-speed anisotropic fine processing without use of any resist.

When the above method is used, the substrate is irradiated with light ina high vacuum, and hence it is possible to prevent contamination of alight irradiation window.

The processing method of the present invention that can achieve theabove objects may also comprise the steps of;

subjecting the surface of a semiconductor substrate or the surface of asubstrate formed of a semiconductor, a metal or an insulator, toselective irradiation with a synchrotron orbit radiation so thatelectron donative properties of the surface are changed to give thedesired pattern; and

selectively depositing a metal film on the surface endowed with saidelectron donative properties.

The apparatus used for carrying out this method is an apparatus forfabricating a semiconductor device, capable of carrying out all thesteps for fabricating a semiconductor device in a series of vacuumvessels that can be evacuated, which comprises;

a load lock chamber in which a specimen is brought under reducedpressure or brought back under atmospheric pressure;

a film forming chamber that can be vacuum-sealed;

an etching chamber that can be vacuum-sealed;

a latent image forming chamber in which surface photo-modification iscarried out, that can be vacuum-sealed and has a light incident window;

a metal-film depositing chamber in which a metal film is selectivelydeposited, that can be vacuum-sealed;

a cleaning chamber in which the surface of the substrate is washed, thatcan be vacuum-sealed; and

a vacuum gate valve through which adjoiningly located chambers of saidchambers are connected with each other.

In the above method, as an additional characteristic feature, the stepof selectively depositing a metal may be carried out by a chemicalgaseous phase growth process making utilization of an alkylaluminumhydride and hydrogen. The alkylaluminum hydride may preferably bedimethylaluminum hydride.

In a more specific embodiment, the surface of a substrate formed of asemiconductor, a metal or an insulator is selectively irradiated with asynchrotron orbit radiation in a reactive gas atmosphere tophotochemically change the properties of the irradiated surface(formation of a latent image layer), thereby to change electron donativeproperties of the surface. Then a gas comprising the alkylaluminumhydride is fed to the surface so that an aluminum film or a metal filmmainly composed of aluminum is selectively formed only on theelectron-donative surface. An electrode or wiring can be thus formed.

According to the above method, the synchrotron orbit radiation iscontinuous light having a very broad wavelength region, ranging fromX-rays to infrared rays, and hence the wavelength can be selectedwithout changing a light source with changes of films to be irradiated.In addition, since the electrode or wiring can be formed without use ofany resist at all, the process can be simplified and the dust that maybe otherwise caused by a stripped resist is not produced. Moreover,since no etching step is required, no after-corrosion occurs, bringingabout an improvement in the performance and yield of devices.Furthermore, since the aluminum or the metal mainly composed of aluminumis deposited by heat CVD, films with a good quality and good surfacecovering properties can be formed by deposition at a high rate.

The processing method of the present invention that can achieve theabove objects may also comprise the steps of;

subjecting the surface of a substrate to selective irradiation withlight after the desired circuit pattern in an atmosphere of a modifyinggas capable of modifying the surface, while maintaining the temperatureof said surface of the substrate to a given temperature range withinwhich a pressure of said modifying gas reaches a saturated vaporpressure, to form on said surface of the substrate a surface-modifiedlayer having a pattern structure; and

etching the surface-unmodified layer using said surface-modified layeras a protective film.

The processing method may also include;

those wherein, in the step of forming the surface-modified layer, thesubstrate surface is oxidized to form a surface-oxidation-modifiedlayer;

those wherein, in the step of forming the surface-modified layer, thesubstrate surface is nitrided to form a surface-nitridation-modifiedlayer; and

those wherein, in the step of etching, the etching is effected at anetching selection ratio larger than the ratio of the thickness of thesurface-unmodified layer to the thickness of the surface-modified layer.

The processing method may also further comprise the step of cleaning thesurface of the substrate before the step of forming the surface-modifiedlayer.

The processing apparatus of the present invention that can achieve theabove objects may also be a fine-processing apparatus comprising a lightsource, a latent image forming chamber in which the surface of asubstrate is irradiated with light emitted from said light source toform a surface-modified layer on said surface of the substrate, and anetching chamber in which said surface of the substrate is etched,wherein;

said apparatus further comprises an evacuating means capable ofevacuating each of said latent image forming chamber and said etchingchamber to a given pressure;

said latent image forming chamber comprises a modifying gas feedingmeans for feeding into said latent image forming chamber a modifying gascapable of modifying the surface of the substrate, a holder that holdssaid substrate and is provided with a temperature controlling meanscapable of controlling the temperature of said substrate to atemperature at which a pressure of said modifying gas in said latentimage forming chamber reaches a saturated vapor pressure of saidmodifying gas, and an optical system for selectively irradiating saidsurface of the substrate with light of said light source after thedesired circuit pattern; and

said etching chamber comprises a holder that holds the substrate onwhich said surface-modified layer is formed, and an etching gas feedingmeans for supplying to said surface of the substrate an etching gas thatetches the surface-unmodified layer using said surface-modified layer asa protective film.

This apparatus may also be those wherein;

said latent image forming chamber and said etching chamber are connectedwith each other through a gate valve through which said substrate can betransported;

said optical system provided in said latent image forming chambercomprises a mask on which a mask pattern has been formed after thecircuit pattern so that the surface of the substrate is irradiated withthe light of said light source through said mask to form a mask patternimage on said surface of the substrate;

said modifying gas feeding means is provided with a gas excitation meansthat excites the modifying gas and supplies the resulting active speciesto the surface of the substrate;

said etching gas feeding means is provided with a plasma generationmeans that makes the etching gas into plasma and supplies the plasma tothe surface of the substrate;

said etching gas feeding means excites the etching gas and supplies theresulting active species to the surface of the substrate; and

a cleaning chamber comprising a holder that holds the substrate and acleaning gas feeding means that excites a cleaning gas for washing thesurface of said substrate or makes the gas into plasma and supplies theexcited gas or the plasma to the surface of said substrate, is furtherconnected with said latent image forming chamber through a gate valvethrough which said substrate can be transported.

As a matter of course, these additional modes can be used independentlyor in appropriate combination.

In the above processing method, the modifying gas is brought into thestate that the vaporization and solidification are balanced on thesurface of the substrate while maintaining the temperature of thesubstrate to a temperature at which a pressure of the modifying gasatmosphere reaches a saturated vapor pressure of the modifying gas, sothat the molecules of the modifying gas can be adsorbed to the substatesurface efficiently. The selective irradiation of the substrate surfaceadsorbed with the modifying gas molecules with light after the circuitpattern causes photochemical reaction at the part irradiated with light,so that the surface-modified layer after the circuit pattern is formed.The etching is then effected using the surface-modified layer as aprotective film, so that the surface-unmodified part except thesurface-modified layer is removed on the substrate surface and thus thesurface-modified layer remains as a pattern.

In the above apparatus of the present invention, the modifying gas issupplied into the latent image forming chamber, where the modifying gasin the latent image forming chamber is maintained to a given pressureand the temperature of the substrate is so controlled that this pressurereaches a saturated vapor pressure of the modifying gas. Thus themolecules of the modifying gas are adsorbed on the substrate surface.The resulting substrate surface is selectively irradiated with lightafter the circuit pattern, thereby causing the photochemical reaction toform the surface-modified layer after the circuit pattern. Subsequently,the substrate on which the surface-modified layer has been formed ismoved to the etching chamber and the substrate surface is exposed to theetching gas having been excited or made into plasma, so that thesurface-unmodified part is removed from the substrate surface and thesurface-modified layer remains as a pattern. Since the above latentimage forming chamber and etching chamber are connected through the gatevalve, the substrate can be transported without its exposure to theatmosphere. In the instance where the apparatus is provided with thecleaning chamber connected with the latent image forming chamber, thesubstrate on which the pattern is to be formed can be washed. Inaddition, since the cleaning chamber and the latent image formingchamber are connected through the gate valve, the pattern formation onthe substrate can be made to proceed in a clean state without adhesionof dust or the like, after the cleaning has been carried out.

EXAMPLES

Examples of the present invention will be described below with referenceto the accompanying drawings.

Example 1

FIGS. 1A to 1D are diagrammatic cross sections to stepwise illustrate aprocedure for pattern formation according to the first embodiment of theprocessing method of the present invention. The procedure will bedescribed in order of the drawings that start from FIG. 1A. Referencenumeral 101a denotes a sample, comprising a 3,000 Å thick amorphoussilicon nitride (a-SiN) film 103 formed a quartz glass substrate 102 byplasma CVD (FIG. 1A). The sample 101a shown in FIG. 1A is irradiatedthereon with beams 105 of argon ions (Ar⁺) and thereby asurface-modified layer 104 having sustained damage due to the argon ionsis formed on the surface of the a-SiN film 103 to give a sample 101b(FIG. 1B). Next, the sample 101b is irradiated with KrF excimer laserlight 107, so that a latent image layer 106 is formed in thesurface-modified layer 104 to give a sample 101c (FIG. 1C).Subsequently, the sample is etched with chlorine plasma streams 108 byuse of the latent image layer 106 as a mask, and thus a sample 101dhaving the desired pattern form can be obtained (FIG. 1D).

FIG. 2 is a diagrammatic cross section to illustrate the constitution ofan apparatus for carrying out the above procedure of fabrication. Thisapparatus is provided with a latent image forming chamber 112bpositioned at the middle as shown in the drawing, a surface-modifiedlayer forming chamber 112a (left side in the drawing) serving as aprocessing chamber, and an etching chamber 112c (right side in thedrawing). In the surface-modified layer forming chamber 112a, asurface-modified layer is formed on the surface of the sample. In thelatent image forming chamber 112b, a latent image is formed on thesurface-modified layer formed on the surface of the sample in thesurface-modified layer forming chamber 112a. In the etching chamber112c, the sample is etched. The surface-modified layer forming chamber112a and latent image forming chamber 112b, and the latent image formingchamber 112b and etching chamber 112c, are connected with each otherthrough a gate valve 110b and a gate valve 110c, respectively. Thesurface-modified layer forming chamber 112a is provided with a gatevalve 110a through which the sample 101a is put in or out from theoutside, and transport means (not shown) for transporting the sample101a to 101c between adjoining chambers are provided through therespective gate valves 110a, 110b and 110c. Thus, the sample 101 can bemoved through each chamber without its exposure to the atmosphere, andhence it becomes possible to prevent adhesion of dust to the sample 101or concurrent deterioration of the device.

In the following, to describe the constitution of each chamber, theletter symbol a, as a rule, will be attached to the end of the referencenumeral for the members that constitute the surface-modified layerforming chamber 112a; b, for the members that constitute the latentimage forming chamber 112b; and c, for the members that constitute theetching chamber 112c. In the drawing, reference numerals 109a, 109b and109c denote sample holders that hold the sample 101; 111a, 111b and111c, gas inlets from which processing gases are fed to the respectiveprocessing chambers; 113a and 113c, plasma chambers in which the plasmaof modifying gas or etching gas, respectively, is generated; 114a and114c, magnetic coils for producing magnetic fields inside the plasmachambers 113a and 113c, respectively; 115a and 115c, cooling waterinlets from which cooling water for cooling the magnetic coils 114a and114c and the plasma chambers 113a and 113c, respectively; 116a and 116c,cooling water outlets; 117a and 117c, microwave transmission windowsthrough which microwaves are supplied to the plasma chambers 113a and113c, respectively; 118a, a group of electrodes for withdrawing ionsfrom the plasma generated in the plasma chamber 113a to accelerate theminto the desired energy; 119, a KrF excimer laser serving as a lightsource; 120, an illumination optical system for illuminating a maskcomprised of a quartz plate (or a reticle) patterned with Cr; 122, aprojection optical system for forming an image of the mask pattern onthe surface of the sample 101; and 123b, a window made of quartz,through which the light having come out of the projection optical system122 is led into the latent image forming chamber 112b.

An example of the procedure of pattern formation using the apparatusshown in FIG. 2 will be described below.

First, a method of forming the surface-modified layer 104 by irradiationwith the argon beams 105 on the surface of the a-SiN film 103 as shownin FIG. 1B will be described. The sample 101a was fed into the aforesaidsurface-modified layer forming chamber 112a through the gate valve 110aand placed on the sample holder 109a. Then a vacuum exhaust system (notshown) was operated to evacuate the insides of the surface-modifiedlayer forming chamber 112a and plasma chamber 113a to 10⁻⁸ Torr or less.Subsequently, argon gas was fed from the gas inlet 111a to the plasmachamber 113a at a flow rate of 20 sccm, and the above vacuum exhaustsystem was so operated as for the pressure of the inside to be adjustedto 2×10⁻⁴ Torr. Next, in order to cool the magnet coil 114a and theplasma chamber 113a, the cooling water was flowed in from the coolingwater inlet 115a and flowed out from the cooling water outlet 116a. Themagnetic coil 114a was electrified to produce a magnetic field in theplasma chamber 113a, and at the same time the microwaves of 2.45 GHz and800 W produced in a microwave generator (not shown) were propagatedusing a waveguide to supply them to the plasma chamber 113a through themicrowave transmission window 117a. As a result, in the plasma chamber113a, the electric field of the microwaves and the magnetic fieldproduced by the magnetic coil 114a accelerated electrons in a goodefficiency to cause ionization of neutrons, so that dense argon plasmawas generated. The plasma was generated in a better efficiency when thesize of the magnetic field was kept to the size of a magnetic field thatcaused electronic cyclotron resonance (875 Gauss in the case of 2.45 GHzmicrowaves; magnetic coil current: 154 A). Next, controlling the voltageapplied to the group of electrodes 118a, Ar⁺ ions were withdrawn fromthe plasma generated in the plasma chamber 113a and were accelerated toan energy of 1 keV. Ion current density at this time was 1 mA/cm². Withbeams of Ar⁺ ion beams thus withdrawn, the a-SiN film 103 of the sample101a was irradiated on its whole surface for 2 minutes. Afterirradiation with the argon beams, the surface-modified layer 104 wasformed in which the damage such as break of a-SiN bonds or occurrence oftraps was produced in a depth of about 30 Å from the surface. The sample101b was thus obtained. After completion of this processing, the gassupply was stopped, and the inside of the surface-modified layer formingchamber 112a was evacuated to give a pressure of 10⁻⁸ Torr or less.

Next, the latent image forming step as shown in FIG. 1C was carried out,i.e., the step of selectively irradiating the surface of thesurface-modified layer 104 of the sample 101b with the laser light 107,thereby causing photochemical reaction only at the part irradiated withthe laser light 107 to modify the surface to form a pattern. The latentimage forming chamber 112b was previously evacuated to 10⁻⁸ Torr or lessby means of a vacuum exhaust system (not shown). Then the gate valve110b was opened, and the sample 101b was transported from thesurface-modified layer forming chamber 112a to the latent image formingchamber 112b and placed on the sample holder 109b. Thereafter, the gatevalve 110b was closed, and the latent image forming chamber 112b wasagain evacuated to 10⁻⁸ Torr or less. Subsequently, O₂ gas was fed fromthe gas inlet 111b into the latent image forming chamber 112b, and thevacuum exhaust system was operated so as for the pressure in the insideto be adjusted to 200 Torr.

Next, with the laser light 107 of 248 nm in wavelength, radiated bymeans of the KrF excimer laser serving as the light source 119, the mask121 to which the desired pattern had been applied was uniformlyirradiated through the illumination optical system 120, and then, withthe light transmitted through the mask 121, the surface of the sample101 was irradiated through the projection optical system 122 and thewindow 123b to form on the surface of the sample 101 an image of thepattern formed on the mask 121. As a material for the window 123b, aquartz plate was used so that the laser light 107 with an wavelength of248 nm was transmitted without being absorbed. On the surface of thesurface-modified layer 104 on which the mask image had been formed, thephotochemical reaction of O₂ with a-SiN took place only at the partirradiated with the laser light 107, so that upon exposure for 5 minutesthe surface-modified layer 104 was patternwise changed into the latentimage layer 106, i.e., an SiO₂ layer. The sample 101c was thus obtained.Since in the present example the surface-modified layer 104 waspreviously formed, the photochemical reaction was accelerated to causeuniform photochemical reaction, and hence the latent image layer 106with densness and a high etching inhibitory power was formed. At thepart not irradiated with the laser light 107, this reaction did notproceed, and thus a negative pattern of the mask 121, comprised of thelatent image layer 106, was formed on the surface of the a-SiN film 103.In other words, a latent image wherein a-SiN was modified to SiO₂ wasformed. The depth of the latent image layer 106 was equal to the depthof the surface-modified layer 104, and the reaction did not proceedbeyond that depth.

After the latent image layer 106 was formed, the supply of O₂ gas wasstopped, and then the inside of the modifying chamber 112a was evacuatedto give a pressure of 10⁻⁸ Torr or less.

Next, the etching step as shown in FIG. 1D was carried out, i.e., thestep of etching away the part other than the latent image layer 106formed in the precedent step, using this layer as a mask. The insides ofthe etching chamber 112c and plasma chamber 113c were previouslyevacuated to 10⁻⁸ Torr or less by means of a vacuum exhaust system (notshown). Then the gate valve 110c was opened, and the sample 101c wastransported from the latent image forming chamber 112b to the etchingchamber 112c and placed on the sample holder 109c. Thereafter, the gatevalve 110c was closed, and the insides of the etching chamber 112c andplasma chamber 113c were again evacuated to 10⁻⁸ Torr or less.Subsequently, Cl₂ gas was fed from the gas inlet 111c into the plasmachamber 113c, and the vacuum exhaust system was operated so as for thepressure in the inside to be adjusted to 5×10⁻⁴ Torr. In order to coolthe magnet coil 114c and the plasma chamber 113c, the cooling water wasflowed in from the cooling water inlet 115c and flowed out from thecooling water outlet 116c. The magnetic coil 114c was electrified at 154A to produce a magnetic field of 875 Gauss in the plasma chamber 113c,and also the microwaves of 2.45 GHz and 400 W generated in a microwavegenerator (not shown) were propagated using a waveguide to supply themto the plasma chamber 113c through the microwave transmission window117c. As a result, in the plasma chamber 113c, chlorine plasma wasgenerated in the same way as the argon plasma previously described. Thechlorine plasma thus generated was accelerated by a scattering magneticfield in the direction of the magnetic line of force, and made into achlorine plasma flow 108, with which the sample 101 was irradiated. TheCl⁺ ions in the plasma were accelerated by floating potential (10 to 20V) produced between the sample 101 and the plasma, and they collidedagainst the surfaces of the surface-modified layer 104 and latent imagelayer 106, so that only the surface-modified layer 104 and the a-SiNfilm 103 beneath it were etched by the excited Cl or Cl₂. The sample101d was thus obtained. The selectivity ratio (a-SiN/SiO₂) representingthe ratio of etching rate for the a-SiN constituting thesurface-modified layer 104 and the SiO₂ constituting the latent imagelayer 106 was about 150, and hence the etching of the a-SiN film 103 wascompleted before the latent image layer 106 serving as a masking memberwas removed. Since, in this etching, the pressure was as low as 10⁻⁴Torr, the mean free path of the ions became ˜8 cm, which was very largerthan that of an ion sheath (˜0.1 mm). Thus, ions with a good verticallinearity were made incident on the surface of the a-SiN film 103, andhence it was possible to effect fine processing (≧0.5 μm) in a goodanisotropy.

In the example described above, the surface-modified layer 104 wasformed by generating ion beams with uniform energy using the plasmachamber 113a, and irradiating the sample with such beams. It, however,was also possible to form the surface-modified layer 104 by using ionshaving a broad energy distribution, contained in plasma produced byhigh-frequency discharging making use of parallel tabular electrodes.

FIG. 3 is a cross section to schematically illustrate an example of theconstitution of the surface-modified layer forming chamber 131 whereinthe surface-modified layer 104 is formed by such ions having a broadenergy distribution. The gate valve that connects this chamber with thelatent image forming chamber is not shown in this drawing. In FIG. 3,reference numeral 132 denotes a sample holder; 133, a gas inlet; 134, aninsulator for insulating the sample holder 132 and the surface-modifiedlayer forming chamber 131 in the direction of direct currents; 135, ahigh-frequency power source of 13.56 MHz and 800 W; 136, a matching boxfor securing impedance matching on the side of the sample holder 132 andthe side of the high-frequency power source 135; 137, an opposingelectrode that opposes the sample holder 132; and 138, a gate valve.

How to operate the formation of the surface-modified layer 104 will bedescribed. The aforesaid sample 101 was placed on the sample holder 132through the gate valve 138, and the inside of the surface-modified layerforming chamber 131 was evacuated to a pressure of 10⁻⁸ or less by meansof a vacuum exhaust system (not shown). Next, Ar was fed at a flow rateof 50 sccm into the surface-modified layer forming chamber 131 from thegas inlet 133, and the vacuum exhaust system was operated so as for thepressure inside the surface-modified layer forming chamber 131 to beadjusted to 0.08 Torr. Next, a high frequency of 13.56 MHz and 800 W wasapplied to the sample holder 132 while making adjustment of the matchingbox 136, to generate plasma in the space between the sample holder 132and the opposing electrode 137. Since the sample holder 132 wasinsulated from the surface-modified layer forming chamber 131 in thedirection of direct currents, a negative DC bias voltage of about -1 kVwas generated between the sample holder 132 and the opposing electrode137 because of the difference in mobility between electrons and ions.Because of this voltage, Ar ions were accelerated and they collidedagainst the surface of the a-SiN film 103, so that the damage wasproduced on the surface of the a-SiN film 103, where thesurface-modified layer 104 was formed. The energy of the ions was about1 keV at maximum, and was distributed over a wide range lower than that.Hence, although it was not a single energy, the same effect as stated inregard to the surface-modified layer forming chamber 112a shown in FIG.2 was obtained. In this instance, the processing was carried out for 5minutes. After completion of the processing, the gas supply was stopped,and the inside of the surface-modified layer forming chamber 131 wasevacuated to a pressure of 10⁻⁸ Torr. Thereafter it was possible tocarry out the latent image formation and the etching in the same way.

In this example, the KrF excimer laser light with a wavelength of 248 nmwas used as the irradiation light for the formation of the latent imagelayer 106. The wavelength of the irradiation light herein used, however,may have a shorter wavelength than the wavelength at which theabsorption begins on the film surface on which the latent image isformed. Since the absorption on the a-SiN became lager at 300 nm orless, it was possible to used a mercury lamp, a heavy hydrogen lamp, anArF excimer laser, a KrCl excimer laser, an F₂ laser, etc.

The etching in the present example was so designed as to be carried outusing the chlorine plasma flow generated by accelerating chlorineplasma, in order to effect fine processing. When, however, the fineprocessing is not particularly required, the etching may be carried outusing an excited gas in the etching chamber 141 as shown in FIG. 4. InFIG. 4, reference numeral 142 denotes a gas inlet from which the etchinggas is fed in; 143, a microwave gas exciting device for generatingplasma by producing a microwave electric field to form excited species;144, a transport pipe made of quartz, through which the excited gasgenerated in the microwave gas exciting device 143 is transported to theetching chamber 141; 145, a sample holder; and 146, a gate valve.

Operation of the etching in the etching chamber 141 will be described.First, the etching chamber 141 was previously evacuated to a pressure of10⁻⁸ Torr or less by means of a vacuum exhaust system (not shown). Thegate valve 146 was opened, and the sample 101 was transported from thelatent image forming chamber 112b in the same way as in the processpreviously described, and placed on the sample holder 145. Then the gatevalve 146 was closed, and the etching chamber 141 was again evacuated toa pressure of 10⁻⁸ Torr or less. Next, Cl₂ gas, the etching gas, was fedat a flow rate of 500 sccm into the microwave gas exciting device 143from the gas inlet 142, and then the vacuum exhaust system was operatedso as for the pressure in the etching chamber 141 to be adjusted to 0.25Torr. Subsequently, microwaves of 2.45 GHz and 400 W generated in amicrowave generator (not shown) were supplied to the microwave gasexciting device 143, where Cl₂ gas was made into plasma, and the excitedmolecules Cl₂ ⁺, Cl⁺, excited by making the gas into plasma weresupplied to the etching chamber 141 through the transport pipe 144. Uponreach of the excited molecules Cl₂ ⁺, Cl⁺ to the surface of the sample101, the a-SiN film 103 was etched using the latent image layer 106 as amask. It was thus possible to obtain the sample 101d. Since the etchingcarried out here was attributable to pure chemical reaction making useof the above excited species, no damage was produced, but the etchingisotropically proceeded and hence a fine-processing performance wassacrificed.

In the present example, the respective processing chambers wereconnected through the gate valve. The present invention can also beworked even with use of respectively independent apparatus.

Example 2

In the present example, an n⁺ semiconductor layer is formed on poly-Sito give the surface-modified layer. The present example will bedescribed below. In the present example, the a-SiN film 103 as shown inFIG. 1A is replaced with a poly-Si film formed by low pressure CVDmethod in a thickness of 3,000Å, and also P⁺ ion beams are used in placeof the Ar⁺ ion beams 105. The apparatus is constructed in the same wayas the apparatus shown in FIG. 2. Thus the procedure of fabrication willbe described below with reference to FIG. 2.

Formation of the n⁺ layer on the surface of the poly-Si film in thepresent example is carried out in the same way as the step of formingthe surface-modified layer 104 using the Ar⁺ ion beams 105 in Example 1.A sample used in the present example was placed on the sample holder109a through the gate valve 110a, and the insides of thesurface-modified layer forming chamber 112a and plasma chamber 113a wereevacuated to a pressure of 10⁻⁸ Torr or less by means of a vacuumexhaust system (not shown). Next, PH₃ gas was fed at a flow rate of 20sccm from the gas inlet 111a into the plasma chamber 113a, and thevacuum exhaust system was so operated as for the pressure in the chamberto be adjusted to 2×10⁻⁴ Torr. Subsequently, the magnetic coil 114a waselectrified at 154 A to produce a magnetic field of 875 Gauss in theplasma chamber. Next, the microwaves of 2.45 GHz and 800 W generated ina microwave generator (not shown) were propagated using a waveguide tosupply them to the plasma chamber 113a through the microwavetransmission window 117a. As a result, in the plasma chamber 113a, PH₃plasma was generated. Ion species present in the plasma were PH₃ ⁺, PH₂⁺, PH⁺, P⁺, H₂ ⁺ and H⁺. Next, controlling the voltage applied to thegroup of electrodes 118a, these ions were withdrawn from the plasmagenerated in the plasma chamber 113a and accelerated to an energy of 1keV. Ion current density at this time was 0.6 mA/cm². With beams of Ar⁺ion beams thus withdrawn, the poly-Si film of the sample was irradiatedon its whole surface for 3 minutes 30 seconds. This irradiation causedphosphorus atoms to invade as impurities in a depth of about 30 Å fromthe surface, which served as a doner to form an n⁺ semiconductor layer.Since the n⁺ semiconductor commonly tended to be oxidized, thesubsequent step of forming a latent image was more accelerated. Aftercompletion of this processing, the gas supply was stopped, and theinside of the surface-modified layer forming chamber 112a was evacuatedto give a pressure of 10⁻⁸ Torr or less.

As subsequent steps, the step of forming a latent image as shown in FIG.1C and the step of etching as shown in FIG. 1D were carried out in thesame manner as in Example 1, so that it was possible to form the desiredpattern.

Example 3

Example 3 of the present invention will be described below.

FIGS. 5A to 5D are diagrammatic cross sections to stepwise illustrate aprocedure for fabricating an amorphous silicon photosensor.

First, as shown in FIG. 5A, on the top surface of a substrate 151comprised of quartz glass, a Cr film 152 with a thickness of 1,000 Å wasdeposited. Subsequently, the Cr film 152 was etched into the desiredpattern to form a lower electrode 153 as shown in FIG. 5B. In theformation of the lower electrode 153, like the manner as described inExample 1, a surface-modified layer was formed using Ar⁺ ion beams withan energy of 2 keV, and thereafter the layer was selectively irradiatedwith KrF excimer laser light to partially form a latent image layercomprised of CrO_(x), followed by etching with Cl₂ gas used as etchinggas, using the latent image layer as a mask.

Next, as shown in FIG. 5C, films up to an Al film 157 were successivelydeposited. The films were deposited in the procedure as follows: Thesubstrate as shown in FIG. 5B was heated to 350° C., and an a-SiN film154 with a thickness of 3,000 Å was formed on the surface of thesubstrate by plasma CVD making use of a mixed gas of SiH₄, NH₃ and H₂.Subsequently, using a mixed gas of SiH₄ and H₂, an a-Si film 155 with athickness of 1.5 μm was formed by plasma CVD. Next, on the top surfacethereof, an n⁺ a-Si film 156 with a thickness of 2,000 Å was formedusing a mixed gas of SiH₄, PH₃ and H₂, and the Al film 157 with athickness of 6,000 Å was further formed thereon.

Next, as shown in FIG. 5D, a light incidence opening 159 was provided atthe middle of the Al film 57, and the film was processed so that thecircumference of the opening served as an upper electrode 158. Proceduretherefor was as follows: In the same manner as in Example 1, thesurface-modified layer was formed using Ar⁺ ion beams with an energy of2 keV, and thereafter the layer was selectively irradiated with KrFexcimer laser light to partially form a latent image layer comprised ofAlO_(x), followed by etching with Cl₂ gas used as etching gas, using thelatent image layer as a mask, to a depth reaching the n⁺ a-Si film 156.As a result, the light incidence opening 159 and the upper electrode 158were formed.

Thus, in the present example, it was possible to fabricate the devicewithout use of the resist having been hitherto used. Hence thefabrication steps was greatly simplified, and it was possible tofabricate the amorphous silicon photosensor without causing a decreasein yield due to dust.

In all the examples described above, examples have been described onthose making use of the Ar+ ion beams or ions having a broad energydistribution, contained in the plasma. They may also be beams having asuitable energy, as exemplified by charged beams and electron beams, andbe by no means limited to those exemplified in the above.

Example 4

Example 4 of the present invention will be described below withreference to the drawings.

FIGS. 6 to 10 are cross sections to diagrammatically illustrate theconstitution of a cleaning chamber 201, a sputtering film formingchamber 202, a plasma film forming chamber 203, an etching chamber 204and a latent image forming chamber 205, respectively, that are used incarrying out the present invention.

In FIG. 6 illustrating the cleaning chamber 201, reference numeral 211denotes a gas inlet provided above the cleaning chamber 201 so that acleaning gas is fed into the cleaning chamber 201; 212, a sample holderthat holds a sample 22 placed in the cleaning chamber 201; 213, anopposing electrode that opposes the sample holder 212; 214, an insulatorfor insulating the sample holder 212 from a vacuum chamber thatconstitutes the cleaning chamber 201; and 215, a high-frequency powersource of 13.56 MHz and 200 W, which is electrically connected to thesample holder 212. Reference numeral 216 denotes a matching box formatching the both sides of the sample holder 212 and the high-frequencypower source 215; and 217, a gate valve. In FIG. 7 illustrating thesputtering film forming chamber 202, reference numeral 221 denotes a gasinlet from which the sputtering gas is fed into the sputtering filmforming chamber 202; 222, a sample holder that holds the sample 22placed in the sputtering film forming chamber 202; 223, an opposingelectrode provided opposingly to the sample holder 222 and to which ahigh-frequency electric power is applied; 224, an insulator forinsulating the opposing electrode 223 from a vacuum chamber thatconstitutes the sputtering film forming chamber 202; 225, ahigh-frequency power source of 13.56 MHz and 500 W; 226, a matching boxfor matching the both sides of the sample holder 222 and thehigh-frequency power source 225; 227, a capacitor for insulating theopposing electrode 224 in the direction of direct currents; 228, asputtering target; and 229, a gate valve. In FIG. 8 illustrating theplasma film forming chamber 203, reference numeral 231 denotes a gasinlet from which a deposition gas is fed into the plasma film formingchamber 203; 232, a sample holder that holds the sample 22 placed in theplasma film forming chamber 203; 223, an opposing electrode providedopposingly to the sample holder 232 and to which a high-frequencyelectric power is applied; 234, an insulator for insulating the opposingelectrode 233 from a vacuum chamber that constitutes the plasma filmforming chamber 203; 235, a high-frequency power source of 13.56 MHz and350 W; 236, a matching box for matching the both sides of the sampleholder 232 and the high-frequency power source 235; and 237, a gatevalve. In FIG. 9 illustrating the etching chamber 204, reference numeral242 denotes a sample holder that holds the sample 22 placed in theetching chamber 204; 234, a microwave plasma gas exciting device forgenerating excited gas supplied to the etching chamber 204; 241, a gasinlet from which an etching gas is fed into the microwave plasma gasexciting device 243; 244, a transport pipe through which the excited gasgenerated in the microwave plasma gas exciting device 243 is transportedto the etching chamber 204; and 245, a gate valve.

In FIG. 10 illustrating the latent image forming chamber 205 in whichsurface modification is carried out, reference numeral 251 denotes a gasinlet from which a modifying gas is fed into the latent image formingchamber 205; 252, a sample holder that holds the sample 22 placed in thelatent image forming chamber 205; 253, a KrF excimer laser serving as alight source; 254, an illumination optical system for illuminating amask 255 comprised of a quartz substrate (or a reticle) patterned withCr; 256, a projection optical system for forming an image of the maskpattern on the surface of the sample 22; 257, a window through which thelight having come out of the projection optical system 256 is led intothe latent image forming chamber 205; and 258, a gate valve. Of theabove apparatus, the light source 253, the illumination optical system254, the mask 255, the projection optical system 256 are provided abovethe latent image forming chamber 205.

FIGS. 11A and 11B are diagrammatic cross sections to stepwise illustratea procedure for forming an Al electrode pattern on a quartz substrate261 according to the present example. FIGS. 11C and 11D are crosssections to respectively show states in which the films shown in FIGS.11A and 11B have been etched.

The present example will be described with reference to FIGS. 6 to 10and FIGS. 11A to 11D.

The quartz substrate 261, shown as the sample 22 in FIGS. 6 to 10, wasplaced on the sample holder 222 of the sputtering film forming chamber202 shown in FIG. 7. Subsequently, the inside of the sputtering filmforming chamber 202 was evacuated to a pressure of 10⁻⁷ Torr or less bymeans of a vacuum exhaust system (not shown). Ar gas was fed into thesputtering film forming chamber 202 from the gas inlet 221, and thevacuum exhaust system (not shown) was operated so as for the pressure inthe sputtering film forming chamber 202 to be adjusted to 0.5 Torr. Acurrent with a high-frequency of 13.56 MHz and 500 W was applied to theopposing electrode 223 while controlling the matching box 226, togenerate plasma in the space between the sample holder 222 and theopposing electrode 223, to effect plasma decomposition of the gas fedtherein, and to sputter an aluminum target attached to the opposingelectrode 223 as a sputtering target, and thus, as shown in FIG. 11A, afilm 262 to be etched, comprised of an Al film with a thickness of 3,000Å, was formed on the quartz substrate 261.

Subsequently, this quartz substrate 261 was subjected to surfacecleaning in the following way, in the cleaning chamber 201 shown in FIG.6. The sample was placed on the sample holder 212, and the inside of thechamber was evacuated to a pressure of 10⁻⁷ Torr or less by means of avacuum exhaust system (not shown). From the gas inlet 211, a gas forcleaning the surface of the sample, i.e., Ar gas in this instance, wasfed at a flow rate of 50 sccm into the cleaning chamber 201, and thevacuum exhaust system (not shown) was operated so as for the pressure inthe cleaning chamber 201 to be adjusted to 0.08 Torr. Next, a currentwith a high-frequency of 13.56 MHz and 100 W was applied to the sampleholder 212 while making adjustment of the matching box 216, to generateplasma in the space between the sample holder 212 and the opposingelectrode 213. Since the sample holder 212 was insulated by a capacitor(not shown) in the direction of direct currents, a negative DC biasvoltage of about -60 V was generated between the sample holder 212 andthe opposing electrode 213 because of the difference in mobility betweenelectrons and ions. Because of this voltage, Ar ions were acceleratedand they collided against the surface of the film 262 to be etched, sothat the stain present on the surface was physically removed bysputtering and thus a cleaned surface was obtained. The processing timewas about 60 seconds.

Next, in order to partially form the surface-modified layer on thesurface of the film 262 to be etched, selective irradiation with lightin a modifying gas atmosphere was carried out in the latent imageforming chamber 205 shown in FIG. 10. In this instance, an AlO_(x) filmthat served as a protective film (an etching mask) in the etchingcarried out later was formed in the following way: The quartz substrate261 was placed on the sample holder 252, and the inside of the latentimage forming chamber 205 was evacuated to a pressure of 10⁻⁷ Torr orless by means of a vacuum exhaust system (not shown). NO₂ gas was fedfrom the gas inlet 251 into the latent image forming chamber 205, andthe vacuum exhaust system was operated so as for the inside pressure tobe adjusted to 1 Torr. Next, with the laser light of 248 nm inwavelength, radiated by means of the KrF excimer laser serving as thelight source 253, the mask 255 was uniformly irradiated through theillumination optical system 254, and then an image of the pattern formedon the mask 255 was formed on the surface of the Al film through thewindow 257 by means of the projection optical system 256. As a materialfor the window 257, quartz was used so that the laser light with anwavelength of 248 nm was transmitted without being absorbed. On thesurface of the film 262 to be etched on which the mask image had beenformed, the photochemical reaction of NO₂ with Al took place only at thepart irradiated with the light, so that upon exposure for 10 minutes afirst protective film 263 comprised of AlO_(x) with a thickness of 10 Åwas partially (patternwise) formed on the surface of the film 262 to beetched, as shown in FIG. 11A. At the part not irradiated with the light,this reaction did not proceed, and finally a negative pattern of themask was formed on the surface of the film 262 to be etched. In otherwords, Al was modified to AlO_(x) and the latent image was formed. TheKrF excimer laser was used here as the light source 253. The same effectwas also obtained when lamp light sources such as a xenon lamp and ahigh-pressure mercury lamp or ultraviolet lasers such as an ArF excimerlaser, an XeCl excimer laser and an Ar laser were used.

Since the first protective film 263 formed in this way did not have asufficient layer thickness, the quartz substrate 261 was again processedin the sputtering film forming chamber 202 shown in FIG. 7 under thesame conditions to form on its surface an aluminum film with a thicknessof 50 Å as a film 264 to be etched. Then the surface thus processed wascleaned in the cleaning chamber 201 shown in FIG. 6 under the sameconditions previously described. Thereafter, in the latent image formingchamber 205 shown in FIG. 10, as a second protective film 265 an AlO_(x)film with a thickness of 10 Å was formed under the same conditionspreviously described, at the same position as the first protective film263 as shown in FIG. 11B. As a result, the first protective film 263 andthe second protective film 264 were 20 Å in total thickness.Subsequently, the resulting sample was subjected to chemical dry etchingin the following way in the etching chamber 204 shown in FIG. 9. Thequartz substrate 261 was placed on the sample holder 242, and the insideof the etching chamber 204 was evacuated to a pressure of 10⁻⁷ Torr orless by means of a vacuum exhaust system (not shown). A gas, Cl₂ in thisinstance, for etching the films 262 and 264 to be etched on which thelatent image was applied twice, was fed at a flow rate of 500 sccm intothe microwave plasma gas exciting device 243, and the vacuum exhaustsystem (not shown) was operated so as for the pressure in the etchingchamber 204 to be adjusted to 0.2 Torr. Microwaves of 2.45 GHz and 700 Wgenerated using a microwave generator (not shown) were supplied to themicrowave plasma gas exciting device 243 to make the etching gas intoplasma. Excited molecules Cl₂ and Cl, thus excited by the plasma, weresupplied for 120 seconds to the surface of the quartz substrate 261through the transport pipe 244 made of quartz, of 20 cm in whole lengthand 40 mm in inner diameter.

The overall etching selection ratio in this instance, of the films 262and 264 to be etched to the first and second protective films 263 and265 was 150, and hence it was possible to form, after completion ofetching, an Al electrode pattern with a sufficent height, comprised ofthe film 262 having been etched, as shown in FIG. 11D. It was possibleto obtain a sufficient etching depth compared with the depth shown inFIG. 11C which was obtained by etching the film shown in FIG. 11A.

Example 5

FIGS. 12A to 12C are diagrammatic cross sections to stepwise illustratea fabrication procedure used when a pattern of an a-Si film, asemiconductor layer, is formed on an ITO-deposited quartz substrate 271according to Example 5 of the present invention. FIGS. 12D to 12F arediagrammatic cross sections to illustrate states wherein those shown inFIGS. 12A to 12C have been etched, respectively.

This example will be described with reference to FIGS. 6, 8, 10 and 12.

The quartz substrate 271 was placed on the sample holder 232 previouslyheated to 250° C. with a heater (not shown) in the plasma film formingchamber 203 shown in FIG. 8. The inside of the plasma film formingchamber 203 was evacuated to a pressure of 10⁻⁷ Torr or less by means ofa vacuum exhaust system (not shown), and the substrate was heated to atemperature of 250° C. From the gas inlet 231, SiH₄ and H₂ were fed atflow rates of 50 sccm and 500 sccm, respectively, into the plasma filmforming chamber 203, and the vacuum exhaust system (not shown) wasoperated so as for the pressure in the plasma film forming chamber 203to be adjusted to 0.5 Torr. A current with a high-frequency of 13.56 MHzand 50 W was applied to the opposing electrode 233 while controlling thematching box 236, to generate plasma in the space between the sampleholder 232 and the opposing electrode 233, to effect plasmadecomposition of the gas fed therein. Thus an a-Si film with a thicknessof 9,000 Å was deposited as a film 272 to be etched, as shown in FIG.12A.

Subsequently, this quartz substrate 271 was subjected to surfacecleaning in the same manner as in Example 4, in the cleaning chamber 201shown in FIG. 6.

Next, an SiO₂ film that serves as a first protective film in the etchingcarried out later was formed in the same way as in Example 4, in thelatent image forming chamber 205 shown in FIG. 10. As a result, thephotochemical reaction of NO₂ with Si took place only at the partirradiated with the light, so that upon exposure for 10 minutes a firstprotective film 273 comprised of SiO₂ with a thickness of 10 Å waspatternwise formed on the surface of the film 272 to be etched, as shownin FIG. 12A. At the part not irradiated with the light, this reactiondid not proceed, and finally a negative pattern of the mask was formedon the surface of the film 272 to be etched. In other words, a-Si wasmodified to SiO₂ to form a latent image.

Since the first protective film 273 formed in this way did not have asufficient layer thickness compared with the thickness of the film 272to be etched, the substrate was again processed in the plasma filmforming chamber 203 sh ow n in FIG. 8 under the same conditions asprevious ones to form on its surface an a-Si film with a thickness of 50Å. Then the surface of the sample was cleaned in the cleaning chamber201 shown in FIG. 6 under the same conditions as those previously used.Thereafter, in the latent image forming chamber 205 shown in FIG. 10,another layer SiO₂ film was formed under the same conditions as thosepreviously described was formed at the same position as the firstprotective film 273 shown in FIG. 12A. A series of these steps werecarried out twice to form films 274 and 276 to be etched and second andthird protective films 275 an d 277, respectively, as shown in FIGS. 12Band 12C. As a result, all the protective films were 30 Å in totalthickness.

Subsequently, the quartz substrate 271 was subjected to chemical dryetching for 150 seconds under the same conditions as those used inExample 4, in the etching chamber 204 shown in FIG. 9. The overalletching selection ratio in this instance, of the films 272, 274 and 276to be etched to the first to third protective films 273, 275 and 277 was300, and hence it was possible to form, after completion of etching, anetched pattern with the desired height as shown in FIG. 12F.

Example 6

As Example 6, a process of forming an a-Si film pattern like that inExample 5 will be shown below.

The films up to the second protective film 275 (see FIG. 12B) was formedin the same manner as in Example 5. Thereafter, in the plasma filmforming chamber 203 as shown in FIG. 8, a 50 Å thick n⁺ -Si film wasformed under the same conditions as in Example 5 except that H₂ -diluted100 ppm PH₃, SiH₄ and H₂ were fed from the gas inlet 231 at flow ratesof 150 sccm, 5 sccm and 30 sccm, respectively. Thereafter, the surfaceof the film was cleaned under the same conditions as in Example 5 toform a surface-modified layer (thickness of protective film: 30 Å),followed by etching. As a result, it was possible to obtain an a-Si filmwith the desired pattern as shown in FIG. 12F.

Thus, a plurality of the films to be etched, deposited on the substratemay be formed of different materials so long as they can be etched usingthe same etchant.

Other embodiments of the processing method of the present invention willbe described below.

FIG. 13A shows a state wherein a layer 302 comprising a conductivematerial such as Al is formed on a substrate 301 made of quartz or thelike. In the following, a fine-processing method of the presentinvention by which this layer 302 is etched in the desired pattern formwill be described in detail.

An article to be processed, as shown in FIG. 13A, is placed in thedesired gas atmosphere, and the processing surface 311 of the article tobe processed is irradiated with laser light 303 corresponding with thedesired pattern form. (FIG. 13B).

The irradiation with the laser light 303 brings the processing surface311 and the desired gas to photochemical reaction corresponding with thedesired pattern to form a surface-modified layer 304 (FIG. 13C).

Next, the processing surface 311 on which the surface-modified layer 304has been formed is irradiated with laser light 305. As a result, thelaser light is absorbed in the region in which the surface-modifiedlayer 304 has been formed. In contrast thereto, the region in which nosurface-modified layer 304 has been formed reflects the laser light.This brings about a temperature rise at the part of the surface-modifiedlayer 304, and, being in the state of the solid phase, an increase inparticle size or a progress of crystallization, so that a region (aprotective film) 306 with a better etching resistance can be formed.

Using as a mask the protective film 306 thus formed, the surface isdry-etched with Cl₂ gas etc. As a result, the part provided with noprotective film 306 is etched because of a difference in etching ratebetween the protective film 306 and the part provided with no protectivefilm 306.

Dry etching carried out until the protective film 306 disappear bringsabout the state as shown in FIG. 13F. Thus, it is possible to processthe layer 302 into the desired pattern form.

In the present invention, the difference in etching rate is utilized inthis way, and hence the present invention is advantageous for the fineprocessing.

The state shown in FIG. 13D, described above, is a state whereinannealing is applied. This annealing can also be effected even withoutuse of electromagnetic waves.

That is, the increase in particle size or crystallization of thesurface-modified layer 304 can be achieved also when the article to beprocessed is heated (307) using a heater or a technique such aselectromagnetic induction (FIG. 13G).

Example 7

FIGS. 13A to 13F are diagrammatic cross sections to illustrate anotherpreferred embodiment of the present invention. As Example 7, a processof forming an Al electrode pattern on a quartz substrate will bedescribed.

As shown in FIG. 13A, an Al film 302 was formed on a quartz substrate301 by sputtering in a thickness of 1 μm.

Next, in order to form the surface-modified layer, in a modifying gasNO₂ atmosphere the surface of the Al film was selectively irradiatedwith KrF laser light using a mask (not shown) (FIG. 13B). Only at thepart irradiated with the light, the photochemical reaction of NO₂ withAl took place, and upon exposure for 10 minutes an AlO_(x) film 304 witha thickness of 10 Å was formed on the surface of the Al film (FIG. 13C).

In order to improve the resistance to the etching carried out later, theAlO_(x) film thus formed was subjected to the following annealing sothat the film was made stabler and stronger. As described with referenceto FIG. 13D, the sample was irradiated with YAG laser light 305 over thewhole surface. Almost all of the laser light reflected from the Al filmcorresponding to the surface-unmodified layer. On the other hand, thelaser light was absorbed at the AlO_(x) film corresponding to thesurface-modified layer, where the temperature of the AlO_(x) film rose,and, in the solid phase, the particle size increased or crystalizationprogressed, so that as shown in FIG. 13E an AlO_(x) film 306 madestabler and stronger was obtained. Using as a mask the AlO_(x) film 306thus obtained, dry etching making use of Cl₂ gas was carried out untilthe mask disappeared. As a result, it was possible to obtain as shown inFIG. 13F the Al film with the desired pattern.

Example 8

An instance in which a semiconductor layer a-Si:H film pattern is formedon a transparent electrode ITO-deposited quartz substrate will bedescribed as Example 8. The basic formation process is the same as thatof Example 7.

On the above substrate, an a-Si:H film was formed by plasma CVD in athickness of 6,000 Å.

Subsequently, the surface modification was carried out by selectiveirradiation with light 303 under the same conditions as those in Example7. As a result, upon exposure for 10 minutes an SiO_(x) :H film with athickness of 10 Å was formed on the a-Si:H film.

In order to more improve the resistance to the etching carried outlater, the SiO_(x) :H film thus formed was subjected to annealing sothat the film was made stabler and stronger. The annealing was carriedout by selectively irradiating the surface of the SiO_(x) :H film withF₂ laser beam, using a mask (not shown) or two-dimensional scanning. Thelaser light was absorbed at the SiO_(x) :H film, where the temperatureof the film rose, and the particle size increased or crystalizationprogressed in the solid phase, as in Example 7, and besides H wasdetached from the SiH bond or unbonded arms Si- and O combined to becomeapproximate to stoichiometric ratio SiO₂, so that the protective filmmade stabler and stronger. Using as a mask the protective film 306 thusformed, chemical dry etching making use of CF₄ +O₂ gas was carried out.As a result, it was possible to obtain the a-Si:H film with the desiredpattern.

Example 9

An instance in which a pattern is formed on a monocrystalline Sisubstrate will be described as Example 9.

The surface modification was carried out on an Si substrate 311 as shownin FIG. 14A, by selective irradiation with light 313 under the sameconditions as those in Example 7 (FIG. 14B). Upon exposure for 20minutes an SiO_(x) film 314 with a thickness of 10 Å was formed (FIG.14C).

In order to improve the resistance to the etching carried out later, theSiO_(x) film 314 thus formed was subjected to annealing so that the filmwas made stabler and stronger. More specifically, the annealing of theSiO_(x) film was carried out by heating a substrate holder (not shown)as shown in FIG. 14D. As a result, in the SiO_(x) film 314, the particlesize increased or crystalization progressed in the solid phase, so thatas shown in FIG. 14E an SiO_(x) film 316 made stabler and stronger wasobtained. Using as a mask the SiO_(x) film 316 thus formed, chemical dryetching making use of CF₄ +O₂ gas was carried out. As a result, it waspossible to obtain the c-Si substrate with the desired pattern as shownin FIG. 14F.

Still another embodiment of the present invention will be subsequentlydescribed. Examples 10 to 12 described below will be described withreference to FIGS. 15A to 15D.

FIG. 15A shows a step of heating a film 402 on a substrate 401 to applysurface modification. Reference numeral 403 diagrammatically denotes theheating of the film 402 by substrate-heating making use of a heater orthe like; and 404, the heating of the film 402 by irradiation making useof a laser lamp or the like. The heating 404 may also be selectivelyapplied only to surface-modifying regions.

As an embodiment of the photo-processing method of the presentinvention, a patterning process carried out by etching will be shownbelow. FIG. 15B shows a state wherein a film 402 to be processed, havingbeen heated as shown in FIG. 15A, is selectively irradiated with light405 in a modifying gas atmosphere. FIG. 15C shows that as a result ofthe steps shown in FIGS. 15A and 15B a surface-modified layer 406 wasformed by photochemical reaction accelerated by the heating. Thissurface-modified layer 406 has a stronger chemical bond and a largerthickness than a surface-modified layer 407 shown in FIG. 16A, which isformed only by photochemical reaction without the heating. Hence, agreater amount (or depth) of etching can be attained in the case whenthe film 402 to be processed is etched using this surface-modified layer406 is used as a protective film (a mask) than the case when thesurface-modified layer 407 shown in FIG. 16A to which no heating isapplied is used as a protective film.

FIG. 15D shows a state wherein the etching is carried out until theprotective film 406 shown in FIG. 15C has disappeared. FIG. 16E alsoshows a state wherein the etching is carried until the protective film407 shown in FIG. 16A has disappeared. As is seen from comparison ofFIG. 15D with FIG. 16E, the heating of the film to be processed canbring about a so much greater amount of etching.

This embodiment of the present invention will be described below ingreater detail by giving examples.

Example 10

On a transparent electrode ITO-deposited substrate, a pattern of aninsulating layer a-SiN_(x) :H film was formed by etching.

The process therefor will be described with reference to FIGS. 17A to17C and 18.

First, as shown in FIG. 17A, an a-SiN_(x) :H film 422 was formed on anITO 421'-deposited substrate 421 by plasma CVD in a layer thickness of5,000 Å. Using this substrate as a sample, this sample, designated as431, was placed on a sample holder 432 in a surface-modifying deviceshown in FIG. 18, and heated to 400° C. by substrate-heating making useof a heater 433. In this state, O₂ gas was fed into it from a gas inlet434, and a vacuum exhaust system 430 was operated so as for the insidepressure to be adjusted to 1 Torr. A mask 438 was irradiated with UVlight from a low-pressure mercury lamp 436 by means of an illuminationoptical system 437, and then a pattern image of the mask 438 was formedon the surface of the a-SiN_(x) :H film by means of a projection opticalsystem 439.

On the surface irradiated with the UV light, O₂ and a-SiN_(x) :H causedphotochemical reaction accelerated by heat, and upon exposure for 20minutes an S:O_(y) film (426 in FIG. 17B) with a thickness of 20 Å wasformed.

Using as a mask the S:O_(y) film 426 thus formed, chemical dry etchingmaking use of CF₄ +O₂ gas was carried out until the mask disappeared. Asa result, as shown in FIG. 17C, the desired pattern was obtained. Forcomparison, an instance in which the processing was carried out withoutheating the film to be processed is shown in FIGS. 16B and 16F. As isseen from FIGS. 16B and 16F, the pattern as shown in FIG. 16F wasobtained from the formation of the protective film 427 with aninsufficient degree of oxidation and an insufficient thickness, and itwas impossible to obtain the pattern as shown in FIG. 17C.

In this example, the heating temperature was set to 400° C. Needless tosay, other temperatures can also bring about the effect of acceleratingthe photochemical reaction, corresponding with the temperatures. As datafor establishing such effect, FIG. 19 shows dead time in chemical dryetching (the time from the initiation of etching to the disappearance ofa-SiO_(y) films, which serves as values indicating the etchingresistance of SiO_(y) films obtained by surface modification ofa-SiN_(x) :H films, carried out under the same conditions except forchanges of heating temperature.

As other data for indicating the etching resistance of the SiO_(x)films, FIG. 20 shows chemical shifts from Si_(2p), obtained from surfaceanalysis by XPS (X-ray photoelectron spectroscopy). As is seen from thedrawings, the more the values of chemical shifts approach to SiO₂ (4.5eV), the more the oxidation proceeds and the higher the etchingresistance becomes.

Example 11

On a quartz substrate, an Al electrode pattern was formed by etching.The process therefor will be described with reference to FIGS. 21A to21C and 22.

As shown in FIG. 21A, an Al film 462 was formed on a quartz substrate461 by sputtering in a thickness of 1 μm. Using this substrate as asample, this sample, designated as 471, was placed on a substrate holder472 in a surface-modifying device shown in FIG. 22, and the sample 471was heated to 500° C. by lamp-heating making use of a halogen lamp 473aand a reflecting plate 473b. In this state, NO₂ gas was fed into it froma gas inlet 474, and a vacuum exhaust system 470 was operated so as forthe inside pressure to be adjusted to 1 Torr. A mask 478 was irradiatedwith light (248 nm) from a KrF laser 476 by means of an illuminationoptical system 477, and then a pattern image of the mask 478 was formedon the Al film surface by means of a projection optical system 479through a window 475.

On the surface irradiated with the light, NO₂ and Al causedphotochemical reaction accelerated by heat, and upon exposure for 10minutes an AlO_(x) film (466 in FIG. 21B) with a thickness of 30 Å wasformed on the surface of the Al film.

Using as a mask the AlO_(x) film 466 thus formed, etching making use ofCl₂ gas was carried out until the mask disappeared. As a result, asshown in FIG. 21C, the desired pattern was obtained.

For comparison, an instance in which the processing was carried outwithout heating the film to be processed is shown in FIGS. 16C and 16G.As is seen from FIGS. 16C and 16G, the pattern as shown in FIG. 16G wasobtained from the formation of the protective film 467 with aninsufficient degree of oxidation and an insufficient thickness, and itwas impossible to obtain the pattern as shown in FIG. 21C.

Example 12

On a transparent electrode ITO-deposited quartz substrate, an a-Sisemiconductor layer was formed and thereafter an Al pattern was formed.In this example, the heating was selectively carried out. The processtherefor will be described with reference to FIGS. 23A to 23C, 24 and25.

As shown in FIG. 23A, an a-Si film 482 was formed on an ITO481'-deposited substrate 481 by plasma CVD in a thickness of 6,000 Å.Using this substrate as a sample 491, this sample was subsequentlyplaced on a substrate holder 492 in a surface-modifying device shown inFIG. 24. In FIG. 24, the substrate holder 492 is set on an XY stage 493that is two-dimensionally movable under control by a computer (notshown). NO₂ gas was fed from a gas inlet 494, and a vacuum exhaustsystem 490 was operated so as for the inside pressure to be adjusted to10 Torr.

A CO₂ laser 496b (a first light source) for heating and a KrF excimerlaser (a second light source) for causing photochemical reaction werecontrolled by a laser control system (not shown) to effect radiation sosynchronized that the both lasers reached a peak power at the same time.Infrared light radiated by means of the CO₂ laser 496b was so adjustedby the projection optical system 497b to give the desired spot size (3μm in the present example) on the sample 491. The infrared light cameout from the projection optical system was reflected by a transmissionreflecting plate 498, and then shed on the sample 491 through the window495. Here, the transmission reflecting plate is made of a syntheticquartz plate with a thickness of 2 mm. Its transmission reflectingsurface is also coated with a high-reflecting film capable of reflectinglight with a wavelength of 11.7 to 12.5 μm and transmitting light (248nm) radiated from the KrF excimer laser 415.

As for the light (248 nm) radiated from the second light source, the KrFexcimer laser 496a, the light was shed on the sample 491 through thetransmission reflecting plate 498 and the window 495 to give the desiredspot size (3 μm in the present example) like the infrared light radiatedfrom the first light source.

The surface irradiated with the light was heated by the above infraredlight to cause a rise of temperature to 350° C., so that the infraredlight accelerated the photochemical reaction. Two-dimensionally movingthe substrate holder 492 set on the XY stage 493, a pattern of asurface-modified layer SiO_(x) (70 Å) was formed as shown by referencenumeral 486 in FIG. 23B.

This surface-modified layer, SiO_(x) film 486 had undergone sufficientoxidation, also having a layer thickness of 70 Å, and thus served as anon-electron-donor.

Subsequently this sample 491 was placed on a substrate holder 412 of aCVD apparatus for the selective deposition of Al, shown in FIG. 25, saidsample being denoted therein as a sample 411. By the following method,Al was deposited only on the surface of an electron donor and no Al wasdeposited on the non-electron-donor, thus enabling selective depositionof Al.

First, the inside of a deposition chamber 417 was evacuated to apressure of 10⁻⁷ Torr or less by means of a vacuum exhaust system 410.Thereafter, the sample 411 was heated with a heater 413d to 300° C. DMAH(CH₃)₂ AlH, obtained through a material vaporizing system 415 wassupplied from a first gas line of a gas mixer 414, using H₂ as a carriergas, and H₂ was supplied from a second gas line.

DMAH and H₂ were fed from a gas inlet 416 into the deposition chamber417, and the gas mixer 414 and the vacuum exhaust system 410 wereoperated so as for the total pressure in the deposition chamber 417 tobe adjusted to 1.5 Torr and the partial pressure of DHAM to 1.5×10⁻⁴Torr, where the deposition was carried out for 10 minutes.

As a result, as shown in FIG. 23C, Al was not deposited at all on thesurface of the non-electron-donor SiO_(x) film 486 to which the surfacemodification had been applied. Surface analysis made on the surface byAuger electron spectroscopy resulted in no detection of Al. On the otherhand, on the surface of the electron donor a-Si film, an Al film with agood quality, containing no carbon at all (below the limit ofdetection), having a resistivity of 2.7 μΩ·cm, an average wiringlifetime of 1×10³ to 10⁴ hours and a hillock density of 0 to 10 innumber/cm², and also having caused no spikes, was selectively deposited.Thus it was possible to form an electrode with a good quality (488 inFIG. 23C).

For comparison, an instance in which the surface modification and Aldeposition were carried out under the same conditions except that noheating with the CO₂ laser was applied is shown in FIGS. 16D and 16H.The surface-modified layer 487 shown in FIG. 16D was so poor in both thedegree of oxidation and the thickness that it could not serve as thenon-electron-donor, and hence, Al was deposited over the whole surfaceas shown by reference numeral 489 in FIG. 16H, and it was impossible toobtain the desired pattern.

An example of the processing apparatus to which a further embodiment ofthe photo-processing method of the present invention can be applied willbe described below with reference to FIG. 26.

In the drawing, reference numeral 501 denotes a sample to be processed(a substrate); 502, a sample holder set on a two-dimensionally movableXY stage 503 controlled by a computer (not shown); and 504, a processingchamber that can be vacuum-sealed. Reference numeral 505 denotes a gatevalve through which the sample 501 can be carried in, or out of, theprocessing chamber 504 and that can be vacuum-sealed; 506, a gas inletfrom which a reactive gas is fed into the processing chamber 504; 507, avacuum exhaust system provided with functions of evacuating the insideof the processing chamber 504 and of keeping constant the pressure ofthe reactive gas fed into the processing chamber 504; and 508, atransmission window through which processing light is transmitted.Reference numeral 509 denotes a CO₂ laser for carrying outphoto-excitation of a first light source, NH₃ laser 510; 511a and 511b,shutters; 512a and 512b, beam correctors for eliminating time andspatial coherency of laser light to make up uniform laser light; and513a and 513b, projection optical systems. Reference numeral 514 atransmission reflecting plate for mixing two light rays having differentwavelengths; 515, a KrF excimer laser, a second light source. Referencenumeral 516 denotes a laser control system for controlling the CO₂ laser509 and the KrF excimer laser 515; 517, a shutter control system forcontrolling the shutters 511a and 511b.

An example of a photo-processing procedure making use of this apparatuswill be described. First, the gate valve 505 is opened to place thesubstrate 501 on the sample holder 502, and the gate valve 505 isclosed. Here, the substrate may be a single body, or may be comprised ofa base member and a deposited film or the like formed thereon.

The vacuum exhaust system 507 is operated to evacuate the inside of theprocessing chamber 504 to have the desired pressure. Next, the reactivegas is fed from the gas inlet 506 into the processing chamber 504, andthe vacuum exhaust system 507 is operated so as for the inside pressureto be adjusted to the desired pressure. The laser control system 516 isoperated to control the CO₂ laser 509 and the KrF excimer laser toeffect radiation so synchronized that the both lasers reached a peakpower at the same time. The light radiated from the CO₂ laser 509 ismade incident on an NH₃ cell provided in the NH₃ laser 510 to causeexcitation of NH₃ gas so that light with a wavelength peculiar to NH₃gas is radiated. The light with this wavelength must be capable ofexciting the vibration of molecules that constitute the surface of thesubstrate. Since the mode of vibration corresponds with that of themolecules constituting the surface of the substrate, the light can beresonantly absorbed, so that the reaction of the substrate with thereactive gas can be accelerated. The light radiated from the first lightsource NH₃ laser 510 enters the shutter 511a, and is modulated accordingto the opening or closing of the shutter, so that the irradiation on thesurface of the substrate 501 can be controlled. The shutters 511a and511b are controlled by the shutter control system 517, for example, socontrolled that they are opened or shut on the same phase. Here, thelight is modulated by controlling the shutters 511a and 511b. The lightcan be modulated also when, without use of the shutters, the radiationfrom the CO₂ laser 509 and the KrF excimer laser 515 is controlled bythe laser control system 516. The modulated light is made to have nocoherency by means of the beam corrector 512a so as to be spatiallyuniform, and then is so adjusted by means of the projection opticalsystem 513a as to give the desired spot size on the substrate 501. Thelight having come out of the projection optical system 513a is reflectedon the transmission reflecting plate 514, passed through the the window508 and shed on the substrate 501. Here, the transmission reflectingplate 514 is made of, for example, a quartz plate with a thickness of 2mm, and its reflecting surface is coated with a high-reflecting filmcapable of reflecting the light with a specific wavelength andtransmitting the light radiated from the KrF excimer laser 515. Thehigh-reflecting film may preferably be comprised of a reflecting filmwith a multi-layer structure comprising an inorganic material. Thewindow 508 is constituted of, for example, an NaCl crystal plate.Besides, KCl crystals, SrF₂ crystals or the like may also be used as thematerials for the window.

In the present invention, the light source for the light that excitesthe vibration of the surface molecules constituting the substrate mayspecifically include lasers, lamps, discharge tubes, and synchrotronorbital radiation light (SOR light) generators. The light source is byno means limited to these so long as it can excite the vibration of thesurface molecules constituting the the substrate. As for the lightradiated from the second light source KrF excimer laser 515, it is seton or off with the shutter 511b on, e.g., the same phase with the lightradiated from the first light source, and is made to have no coherencyby means of the beam corrector 512b so as to be spatially uniform. Next,the light is led to the projection optical system 513b, passed throughthe transmission reflecting plate 514 and the window 508, and then shedon the substrate 501 to give the desired spot size in the same way asthe light radiated from the first light source. In the presentinvention, the light source for the light that causes photochemicalreaction of the reactive gas with the substrate may specifically includelasers, lamps, discharge tubes, and synchrotron orbital radiation light(SOR light) generators. The light source is by no means limited to theseso long as it can cause the photochemical reaction of the reactive gaswith the substrate.

Example 13

Using the apparatus shown in FIG. 26, a silicon nitride (SiN) filmformed on a silicon substrate was etched.

Here, as the pulse oscillation type CO₂ laser 509 for exciting the lightfrom the first light source NH₃ laser 510, a laser of 50 W with afrequency of several thousands Hz was used. As the second light source,a KrF excimer laser of 20 W with a frequency of several thousands Hz wasused.

First, the gate valve 505 was opened and the sample Si substrate onwhich the SiN film had been formed was placed on the sample holder 502,and thereafter the gate valve 505 was closed. Next, the vacuum exhaustsystem 507 was operated to evacuate the inside of the processing chamber504 to a pressure of 10⁻⁷ Torr or less. Then Cl₂ gas was fed from thegas inlet 506 into the processing chamber 504, and the vacuum exhaustsystem 507 was operated so as for the inside pressure to be adjusted to50 Torr.

The laser control system 516 was operated to control the CO₂ laser 509and the KrF excimer laser 515 to effect radiation so synchronized thatthe both lasers reached a peak power at the same time. Infrared lightwith a wavelength of 10.6 μm, radiated from the CO₂ laser 509 was madeincident on an NH₃ cell provided in the NH₃ laser 510 to causeexcitation of NH₃ gas so that infrared light with a wavelength of 11.7to 12.5 μm (wave number: 850˜800 cm⁻¹) was radiated.

The light with this wavelength corresponded with the mode of vibration(˜850 cm⁻¹) of Si--N bonds, and hence was resonantly absorbed.

The infrared light radiated from the NH₃ laser 510 entered the shutter511a, was made to have no coherency by means of the beam corrector 512a,and then was so adjusted by means of the projection optical system 513aas to give the desired spot size (3 μm in the present example) on the Sisubstrate 501. The light having come out of the projection opticalsystem 513a was reflected on the transmission reflecting plate 514comprised of a synthetic quartz plate, was passed through the the window508 comprised of an NaCl crystal plate and was shed on the Si substrate501. Here, the reflecting surface of the transmission reflecting plate514 was coated with a high-reflecting film capable of reflecting theinfrared light with a wavelength of 11.7 to 12.5 μm and transmitting thelight (248 nm) radiated from the KrF excimer laser 515.

As for the light (248 nm) radiated from the second light source KrFexcimer laser 515, it was set on or off with the shutter 511b on thesame phase with the infrared light radiated from the first light source,and was passed through the beam corrector 512b. Thereafter, the lightwas led to the projection optical system 513b, passed through thetransmission reflecting plate 514 and the window 508, and then shed onthe Si substrate 501 to give the desired spot size (3 μm in the presentexample) in the same way as the infrared light radiated from the firstlight source. On the substrate surface irradiated with the infraredlight with a wavelength of 11.7 to 12.5 μm and the far ultraviolet lightwith a wavelength of 248 nm, the electrons excited by the ultravioletlight were exchanged with chlorine atoms, which were incorporated intothe SiN film. On the other hand the Si--N bonds in the substrate surfacewere vibrated and excited by the infrared light, so that the rate of thereaction:

    2SiN+4Cl.sub.2 →2SiCl.sub.4 ↑+N.sub.2 ↑

was increased, and it became possible to effect high-rate etching. Forcomparison with a conventional method, the etching was carried outwithout irradiation with the infrared light to confirm that an etchingrate higher about 20 times than the conventional photo-etching processwas obtained in the present example.

During the irradiation, the sample holder 502 set on the XY stage 503was two-dimensionally moved to effect modulation by operating theshutters, whereby it was possible to form an etching pattern on the SiNfilm. It was confirmed that the etching was effected only at the regionirradiated with light, causing no blur of the image, and in a superiorselectivity.

Example 14

As Example 14, an example in which the whole surface of a sample wasirradiated with first light for exciting surface vibration and thenselectively irradiated through a mask (or a reticle) with second lightfor causing photochemical reaction will be shown here.

FIG. 27 schematically illustrates the apparatus used. In the drawing,reference numeral 518 denotes a mask (or a reticle) through which thesurface of a sample 1 is selectively irradiated with the second lightfor causing photochemical reaction; 519, an illumination optical systemfor illuminating the mask. Other components indicated by the samereference numerals as those in FIG. 26 denote the same components.

Using this apparatus, an SiN film formed on an Si substrate was etched.

First, the gate value 505 was opened and the sample Si substrate 501 onwhich the SiN film had been formed was placed on the sample holder 502.Then the gate valve 505 was closed. The vacuum exhaust system 507 wasoperated to evacuate the inside of the processing chamber 504 to have apressure of 10⁻⁷ Torr or less. Thereafter, Cl₂ gas was fed from the gasinlet 506 into the processing chamber 504, and the vacuum exhaust system507 was operated so as for the inside pressure to be adjusted to 50Torr.

The laser control system 516 was operated to control the CO₂ laser 509and the KrF excimer laser 515 to effect radiation so synchronized thatthe both lasers reached a peak power at the same time. In the same wayas in Example 13, the NH₃ laser was operated to take out radiation ofinfrared light with a wavelength of 11.7 to 12.5 μm (wave number: 850 to800 cm⁻), with which the whole surface of the Si substrate was uniformlyirradiated through the beam corrector 512a, the projection opticalsystem 513a and the transmission reflecting plate 514.

As for the light (248 nm) radiated from the second light source KrFexcimer laser 515, it was passed through the beam corrector 512b and theillumination optical system 519, and then the mask or leticle 518 wasuniformly irradiated with the light. The light was further passedthrough the projection optical system 513b, the transmission reflectingplate 514 and the window 508, so that an image corresponding with thepattern of the mask or leticle 518 was formed on the Si substrate.

The whole surface of the substrate was irradiated with the infraredlight with a wavelength of 11.7 to 12.5 μm, where the Si--N bonds on thesurface of the SiN film were vibrated and excited, and in additionthereto, the surface irradiated with the light with a wavelength of 11.7to 12.5 μm was etched under the same reaction as in Example 13.

Example 15

Using the same apparatus as used in Example 14, a latent imagecomprising an oxide film was selectively formed on a Si₃ N₄ film formedon the Si substrate.

In the same way as in Example 14, the gate valve 505 was opened and theSi substrate 501 on which the SiN film had been formed was placed on thesample holder 502. Then the gate valve 505 was closed. The vacuumexhaust system 507 was operated to evacuate the inside of the processingchamber 504 to have a pressure of 10⁻⁷ Torr or less. Thereafter, NO₂ gaswas fed from the gas inlet 506 into the processing chamber 504, and thevacuum exhaust system 507 was operated so as for the inside pressure tobe adjusted to 100 Torr.

Next, in the same way as in Example 14, the whole surface of thesubstrate was irradiated with the infrared light with a wavelength of11.7 to 12.5 μm, and the surface of the Si₃ N₄ film formed on the Sisubstrate was irradiated with the far-ultraviolet light with awavelength of 248 nm. On the whole surface irradiated with the infraredlight, the Si--N bonds on the Si₃ N₄ film surface were vibrated andexcited. On the surface irradiated with the far-ultraviolet light with awavelength of 248 nm, the photochemical reaction proceeded, so that theoxide film was formed only on the surface irradiated with thefar-ultraviolet light. The oxide film formed had a thickness of about 50Å upon irradiation for about 3 minutes. Thereafter the etching wascarried out using as a mask the oxide film thus formed, so that it waspossible to carry out mask-less fine processing.

Example 16

Using an apparatus shown in FIG. 28, an SiO₂ film was etched. In thedrawing, a CO₂ laser 509 for exciting surface molecules is provided witha Fabry-Perot etalon to have the structure that the radiation wavelengthis variable to a certain extent. In the present example, this was usedin such a state that its radiation wavelength is in agreement with awavelength 9.5 at which the vibration of SiO bonds is absorbed.Reference numeral 520 denotes an ArK excimer laser. Other componentsindicated by the same reference numerals as those in FIG. 27 denote thesame components.

In the same way as in Example 14, the gate valve 505 was opened and thesample Si substrate 501 on which the SiO₂ film had been formed wasplaced on the sample holder 502. Then the gate valve 505 was closed.Thereafter the vacuum exhaust system 507 was operated to evacuate theinside of the processing chamber 504 to have a pressure of 10⁻⁷ Torr orless. Next, NF₃ gas and H₂ were fed at flow rates of 400 sccm and 50sccm, respectively, from the gas inlet 506 into the processing chamber504, and the vacuum exhaust system 507 was operated so as for the insidepressure to be adjusted to 2 Torr.

The laser control system 516 was operated to control the CO₂ laser 509and the ArK excimer laser 520 to effect radiation so synchronized thatthe both lasers reached a peak power at the same time. The CO₂ laser wasoperated to take out radiation of infrared light with a wavelength of9.5 μm (wave number: 1,054 cm⁻¹), with which the whole surface of the Sisubstrate was uniformly irradiated through the beam corrector 512a, theprojection optical system 513a and the transmission reflecting plate514.

As for the light (193 nm) radiated from the second light source ArKexcimer laser 520, it was passed through the beam corrector 512b and theillumination optical system 519, and then the mask or leticle 518 wasuniformly irradiated with the light. The light was further passedthrough the projection optical system 513b, the transmission reflectingplate 514 and the window 508, so that an image corresponding with thepattern of the mask or leticle 518 was formed on the Si substrate.

The whole surface of the substrate was irradiated with the infraredlight with a wavelength of 9.5 μm to vibrate and excite the SiO bonds onthe film surface. Meanwhile, on the surface irradiated with thefar-ultraviolet light with a wavelength of 193 nm, etching proceeded ina good efficiency.

The etching rate became larger about 8 times than that of conventionalphoto-etching, and thus it became possible to carry out processing at ahigh speed.

Besides the example described above, it is possible according to thepresent invention to carry out processing such as CVD, cleaning, etc. ata high speed.

A still further embodiment of the processing method according to thepresent invention will be described below with reference to thedrawings. FIG. 29 diagrammatically illustrates another preferredembodiment of the fine-processing apparatus of the present invention.The apparatus shown in FIG. 29 is, roughly stated, comprised of a loadlock zone, a latent image forming zone serving as a surfacephoto-processing zone, and an etching zone.

Here, the load lock zone is not necessarily essential. In the drawing,reference numeral 601 denotes a sample to be processed; 602, a load lockchamber in which the sample 601 is brought to a vacuum environment orreturned to the atmospheric environment; 603a, 603b, 603c and 603d,vacuum exhaust systems. Reference numerals 604a, 604b and 604c denotegate valves through which the sample 601 can be taken in and out andthat can be vacuum-sealed; 605a, 605b, 605c and 605d, gas inlets fromwhich gas is fed in; and 606, a latent image forming chamber. Referencenumerals 607b and 607c denote sample holders; and 608, an XY movementdevice that can two-dimensionally move the sample holder 607b. Referencenumeral 609 denotes a rare gas excimer serving as a light source; 610, aconcave mirror serving as an image-forming optical system; 611, a windowmade of a monocrystalline plate with a thickness of 1 mm; and 612, anoptical system vacuum container for preventing absorption of laserlight. Reference numeral 613 denotes an etching chamber in which thesample is etched; 614, a microwave gas exciting device; 615, a transportpipe through which excited gas generated in the microwave gas excitingdevice 614 is transported to the etching chamber 613. Specific exampleswill be described below.

Example 17

An SiO₂ film with a thickness of 1,000 Å was formed on the Si substrateby thermal oxidation, and fine processing was applied to the SiO₂ film.The processing was carried out using the apparatus shown i n FIG. 29.First, the gate valve 604a was opened, and the sample Si substrate 601was put in the load lock chamber 602. Thereafter the vacuum exhaustsystem 603a was operated so as for the inside of the load lock chamber602 to be adjusted to 10⁻⁸ Torr or less. The latent image formingchamber 606 was previously evacuated to have a pressure of 10⁻⁸ Torr orless by means of the vacuum exhaust system 603b. Subsequently, the gatevalve 604b was opened, and the Si substrate 601 was placed on the sampleholder 607b. After the gate valve 604b was closed, the vacuum exhaustsystem 603b was evacuated so as for the inside of the latent imageforming chamber 606 to be adjusted to 10⁻⁸ Torr or less. T he inside ofthe optical system vacuum container 612 was evacuated to 10⁻² Torr orless by means of the vacuum exhaust system 603d, and also the vacuumexhaust system 603d was operated so as for a difference in pressurebetween the optical system vacuum container 612 and the latent imageforming chamber 606 to be adjusted to 10 Torr or less. Next, an Arexcimer laser 609, the rare gas excimer laser, was actuated to take outlaser light of 50 mJ in energy per pulse, which was converged with theconcave mirror 610. With the light thus converged, the Si substratesurface was irradiated on its region of 5 μm in spot size. The radiatedlight had a wavelength of 126 nm and an energy of 9.8 eV, and hence theSi--O bond energy of the SiO₂ film on the sample surface was larger than8.3 eV, where this bond was cut off to cause deposition of Si. In thisexample, an Si layer with a thickness of 50 Å was formed. An Si layerwith the desired pattern was formed by tow-dimensionally moving thesample holder 607 by means of the XY movement device 608.

After the Si layer with the desired pattern was formed, the gate valve604c was opened. The sample 601 was put in the etching chamber 613 theinside of which had been evacuated to 10⁻⁸ Torr or less by means of thevacuum exhaust system 603c, and placed on the sample holder 607c. Thegate valve 604c was closed, and again the etching chamber 613 wasevacuated to 10⁻⁸ Torr or less by means of the vacuum exhaust system603c. From the gas inlet 605c, etching gas NH₃ and NF₃ were fed at flowrates of 500 sccm and 100 sccm, respectively, into the microwave gasexciting device 614, and the vacuum exhaust system 603c was operated soas for the inside pressure of the etching chamber 613 to be adjusted to0.25 Torr. Microwaves of 2.45 GHz and 700 W, generated by means of amicrowave generator (not shown) were supplied to the microwave gasexciting device 614 so that the etching gas was made to plasma. The gasexcited by plasma was supplied through the transport pipe 615 into theetching chamber 613. As a result, it was possible to selectively etchonly SiO₂ using the Si layer as a mask to form the desired pattern. Itwas possible to carry out this processing at a higher speed than theconventional photoetching and also to obtain a nice etched surface.Since the photo-processing was carried out in a high vacuum, the windowwas not contaminated and it became unnecessary to clean the window.

Example 18

Fine processing was applied to an Si₃ N₄ film deposited on an Sisubstrate. First, the Si₃ N₄ film was formed by heat CVD in a thicknessof 1,000 Å. Subsequently, in the same way as in Example 17, the sampleSi substrate 601 was placed on the sample holder 607b in the latentimage forming chamber 606. Thereafter, in the same way as in Example 17,the surface of the Si substrate 601 was irradiated with Ar excimer laserlight to cause deposition of Si in the desired pattern. The same effectwas also obtained when the Ar excimer laser was replaced with Kr laserlight. The reason therefor is that the Si--N bonds can be readily cutoff because the Kr laser light has a larger energy (8.5 eV) than thebond energy (4.6 eV) of the Si--N bonds of the Si₃ N₄ film. Next,etching was carried out using an apparatus in which the etching systemserving as the etching zone of the apparatus shown in FIG. 29 wasreplaced with a microwave plasma etching system as shown in Fig, 30. InFIG. 30, reference numeral 603e denotes a vacuum exhaust system; 650e, agas inlet; 706e, sample holder; 616, an etching chamber; 617, a plasmachamber in which plasma for etching is generated; and 618, a microwavetransmission window through which microwaves are supplied to the plasmachamber. Reference numeral 619 denotes a magnetic coil for producing amagnetic field in the inside of the plasma chamber 617; 620 and 621, acooling water inlet and a cooling water outlet, respectively, from whichcooling water for cooling the magnetic coil 619 and the plasma chamber617 is fed in and discharged out. Next, in the same way as in Example17, the Si substrate 601 was placed on the sample holder 607e in theetching chamber 616. Subsequently the gate valve 604c was closed, andthe inside of the etching chamber 616 was evacuated to a pressure of10⁻⁸ Torr or less. From the gas inlet 605e, etching gas, CF₆ and C₂ H₄were fed at flow rates of 30 sccm and 30 sccm, respectively, into theplasma chamber 617, and the vacuum exhaust system 603e was operated soas for the inside pressure of the etching chamber 616 to be adjusted to4×10⁻⁴ Torr. In order to cool the magnetic coil 619 and the plasmachamber 617, the cooling water was flowed in from the cooling waterinlet 620 and flowed out from the outlet 621. At the same time, themagnetic coil 619 was electrified to produce a magnetic field in theplasma chamber 617. Microwaves of 2.45 GHz and 500 W generated in amicrowave generator (not shown) were propagated using a wave guide tosupply them to the plasma chamber 617 through the microwave transmissionwindow 618. In the plasma chamber 616, the electric field of themicrowaves and the magnetic accelerated electrons in a good efficiencyto cause ionization of neutrons, so that dense plasma was generated. Theplasma was generated in a better efficiency when the size of themagnetic field was kept to the size of a magnetic field that causedelectronic cyclotron resonance (875 Gauss in the case of 2.45 GHzmicrowaves). The plasma generated in the plasma chamber 617 was spreadfrom the plasma chamber 617 into the etching chamber 616 along themagnetic line of force, and it reached the surface of the Si₃ N₄ film onthe Si substrate 601. Thus, only the Si₃ N₄ film was selectively etched,and, using the Si layer as a mask, it was possible to effect fineprocessing with the desired pattern. It was possible to carry out thisprocessing at a higher speed than the conventional photoetching and alsoto obtain a nice etched surface. Since the gas pressure was as low as4×10⁻⁴ Torr, ions reached the Si₃ N₄ film surface without theirbombardment with other particles, so that it was possible to carry outetching in a good anisotropy. Since also the ion energy was 10 or so eV,it was possible to carry out etching with less damage.

A still further embodiment of the present invention will be describedbelow in detail with reference to the drawings.

FIG. 31 is a schematic cross section of the apparatus according to thepresent invention, which, roughly stated, comprises a load lock zone, anoptical latent image forming zone and an Al selective deposition zone,which are connected with a gate valve adjoiningly each other. In FIG.31, reference numeral 701 denotes a substrate which is a sample; 702, aload lock chamber in which the substrate 701 is brought to a vacuumenvironment or returned to the atmospheric environment; 703a, 703b and703c, vacuum exhaust systems each comprised of a turbo pump, a rotarypump or the like; 704a, 704b and 704c, gate valves through which thesubstrate 701 can be put in and out and that can be vacuum-sealed; 705a,705b and 705c, gas inlets from which gas is fed in; 706b and 706c,substrate holders on which the substrate 701 is placed; 707, a latentimage forming chamber in which a latent image layer is formed; 708a, anelectron synchrotron or electron storage ring that serves as a lightsource; 708b, a light control section from which the light with a singleor plural wavelength(s) (range) that is necessary among synchrotronorbit radiation light is taken out; 709, an illumination optical systemfor illuminating a mask (or a leticle) 710 patterned with alight-screening material; 711, a projection optical system for formingan image after the mask pattern on the surface of the substrate 701;712, a window through which the light coming out of the projectionoptical system 711 is led into the latent image forming chamber 707;713, an Al selective deposition chamber in which Al or a metal mainlycomposed of Al is selectively deposited on the electron-donative partformed on the substrate surface; 714, a heater for heating the substrate701, provided in the substrate holder 706c; 715, a gas mixer in which astarting material gas and a reactive gas are mixed and from which themixed gas is fed into the Al selective deposition chamber 713; and 716,a starting material gas generator for vaporizing an organic metal intothe starting material gas.

In the apparatus shown in FIG. 31, the substrate 701 whose surface hasbeen cleaned is put in the load lock chamber 702 so that the substrate701 can be fed in a vacuum environment, and the vacuum exhaust system703a is operated to evacuated the inside of the load lock chamber 702.Then the gate valve 704b is opened, and the substrate 701 is placed onthe substrate holder 706a in the latent image forming chamber 707. Withthe synchrotron orbit radiation light generated in the light source 708aand controlled by the light control section 708b, the mask 710 used forforming the desired pattern is uniformly irradiated through the window712 to form a pattern image of the mask 709 by means of the projectionoptical system 711. Materials for the window 712 may vary depending onthe wavelength of the light source used, and a window material that doesnot absorb the light with that wavelength and allows it to pass isselected. The vacuum exhaust system 703b is operated to evacuate theinside of the latent image forming chamber 707, and a gas forphotochemically changing the surface (e.g., O₂, O₃ or NO₂ gas when thesurface is intended to be oxidized, or N₂ or NH₃ gas when the surface isintended to be nitrided) is fed into the chamber so that only the partirradiated with the light may selectively undergo photochemical reaction(e.g., oxidation, nitriding, reduction) to form on the surface a latentimage layer with a thickness of about 50 Å to about 100 Å formed of anoxide film or a nitride film, thereby selectively changing electrondonative properties. Selective oxidation or nitriding of the surface ofa metal or semiconductor makes the surface of the metal or semiconductorselectively non-electron-donative. On the other hand, selectivereduction of an oxide film or nitride film of a metal or semiconductormakes the corresponding part electron-donative. The wavelength of thesynchrotron orbit radiation light for causing the photochemical reactionmay be selected according to the materials of the substrates and typesof gases.

Next, the substrate 701 is placed on the substrate holder 706c in the Alselective deposition chamber 713 having been evacuated by means of thevacuum exhaust system 703c, and the step of selectively depositing Al ora metal mainly composed of Al is carried out. In this step in thepresent invention, heat CVD is used so that a good-quality Al film ormetal film mainly composed of Al can be selectively formed on thesubstrate 701 as a conductive deposited film.

Here, to explain the electron donative properties, an electron donativematerial is a material in which free electrons are present in thesubstrate or free electrons are intentionally produced therein, and isexemplified by a material having a surface on which the chemicalreaction is accelerated by its exchange with molecules of the startingmaterial gas, adsorbed to the substrate surface. For example, ingeneral, metals or semiconductors are included to this material. It alsoincludes those wherein a thin oxide film is present on the surface of ametal or semiconductor. It can be included therein since the chemicalreaction takes place upon exchange of electrons between the substrateand adhered material molecules. Such a metal or semiconductor mayspecifically include semiconductors such as monocrystalline silicon,polycrystalline silicon and amorphous silicon; binary, ternary orquaternary Group III-IV compound semiconductors comprised of anycombination of a Group III element Ga, In or Al and a Group IV elementP, As or N; and metals, alloys or silicides thereof, such as tungsten,molybdenum, tantalum, tungsten silicide, titanium silicide, aluminum,aluminum silicon, titanium aluminum, titanium nitride, copper, aluminumsilicon copper, aluminum palladium, titanium, molybdenum silicide andtantalum silicide.

On the substrate having such an electron-donative surface, Al or themetal mainly composed of Al can be deposited only upon simple thermalreaction in a reaction system comprised of the starting material gas andH₂. For example, the thermal reaction in a reaction system comprised ofDMAH (dimethylaluminum hydride) and H₂ is presumed to basically proceedas follows: ##STR1## The DMAH assumes a dimer structure at roomtemperature. It was also confirmed that MMAH₂ (monomethylaluminumhydride) enabled deposition of high-quality Al by thermal reaction, aswill be shown in examples described later.

The above MMAH₂ has a vapor pressure of as low as 0.01 to 0.1 Torr atroom temperature and hence it is difficult to transport the startingmaterial in a large quantity, and its rate of deposition is severalhundred Å/min at maximum in the present invention. Accordingly, it ismost preferred to use DMAH having a vapor pressure of 1 Torr at roomtemperature.

The temperature at which the substrate is heated with the heater 714 todeposit Al should be higher than the temperature at which a startingmaterial gas containing Al can be decomposed, and not higher than 450°C. Stated specifically, the substrate temperature should be 160° C. to450° C. When Al is deposited under such conditions, the rate ofdeposition can be very high, as much as 100 Å/min to 800 Å/min, at aDMAH partial pressure of 10⁻⁴ to 10⁻³ Torr, and hence it is possible toattain a sufficiently high deposition rate for an Al depositiontechnique used for VSLIs. More preferably, the substrate temperatureshould be 270° C. to 350° C. Al films deposited under such conditionscan be Al films with a good quality, capable of being strongly orientedand also causing no hillocks or spikes in the Al film formed on the Simonocrystalline or Si polycrystalline substrate even when heated at 450°C. for 1 hour. Such Al films can also be excellent in electromigrationresistance.

Next, in order to produce starting material gas, liquid DMAH maintainedat room temperature in the gas producing chamber 716 is subjected tobubbling with H₂ or Ar (or other inert gas) serving as a carrier gas toproduce the DMAH used for deposition on the substrate. This istransported to the gas mixer 715. The H₂ serving as the reactive gas isfed from ano ther route to the gas mixer 715. Flow rates of gases are socontrolled that each gas has the desired value of partial pressure, andthe vacuum exhaust system 703c is operated so as for the total pressureto be kept to a given pressure (10⁻³ to 760 Torr).

Thus, the starting material gas and reactive gas are thermally reactedon the heated substrate surface so that the Al or metal mainly composedof Al is selectively deposited on the surface except thenon-electron-donative surface formed in the precedent step, in otherwords, only on the electron-donative surface formed in the precedentstep. The Al-deposited film thus formed has a resistivity of 2.7 μΩ·cmto 3.0 μΩ·cm at room temperature when its layer thickness is 400 Å,which is substantially equal to the resistivity of an Al bulk, thusgiving a continuous and flat film. Here, the pressure at the time offilm formation can be selected within the range of 10⁻³ Torr to 760Torr. Even if the layer thickness is 1 μm, the resistivity can also beapproximately 2.7 μΩ·cm to 3.0 μΩ·cm at room temperature, and asufficiently dense film can be formed even with such a layer thickness.Reflectance in the visible light wavelength region is substantially 80%,and a thin film with a good surface flatness can be formed bydeposition.

As described above, the film obtained by the metal forming method usedin the present invention is dense, has impurities such as carbon in avery small content, has a resistivity comparable to that of a bulk, andalso has characteristics with a very high surface smoothness. Thus, thefilm can have remarkable effect as stated below.

(i) Decrease in Hillocks:

Hillocks are projections produced on the Al surface because of partialmigration of Al when the release of internal stress occurs during thefilm formation. A similar phenomenon may also occur when local migrationtakes place as a result of electrification. The Al film formed by theabove method has little internal stress and also is nearly in amonocrystalline state. Hence, conventional Al films may cause hillocksof 10⁴ to 10⁶ in number/cm² as a result of heating at 450° C. for 1hours. On the other hand, according to the method of the presentinvention, the hillocks can be greatly reduced to 0 to 10 in number/cm2.Thus, since there is little surface irregularities on the Al surface,resist films or interlayer insulating films can be made into thin films.This is advantageous for making films finer and flatter.

(ii) Improvement in Electromigration Resistance:

Electromigration is a phenomenon resulting from the migration of wiringatoms caused by the flowing of high-density currents. This phenomenoncauses generation and growth of voids along grain boundaries, resultingin a decrease in cross sectional areas, which is accompanied with heatgeneration and disconnection of wiring.

The electromigration resistance is commonly evaluated on the basis ofaverage wiring lifetime.

The wiring formed by a conventional method has an average wiringlifetime of 1×10² to 10³ hours (in the case of a wire cross-sectionalarea of 1 μm²) under electrification test conditions of 250° C. and1×10⁶ A/cm². On the other hand, the Al film obtained by the metal filmforming method used in the present invention has achieved an averagewiring lifetime of 10³ to 10⁴ hours in wiring with a cross-sectionalarea of 1 μm².

Thus, according to the method of the present invention, the wiring canbe well suited for practical use if it has a layer thickness of 0.3 μmin the case of a wiring width of 0.8 μm. Namely, since the wiring layerthickness can be made small, the irregularities that may be present onthe surface of a semiconductor after the wiring has been provided can beprevented to a minimum and also a high reliability can be obtained whenusual electric currents are flowed. In addition, a very simple processcan be satisfactory for the purpose.

As described above in detail, employment of the above method in themethod of forming the wiring of a semiconductor integrated circuits canbring about a great improvement in yield and a promotion of costreduction, compared with conventional Al wiring.

Employment of this method also makes it possible to greatly simplify thefabrication process and form Al electrodes or wiring in a good qualitywithout use of photolithography or etching making use of a resist, sothat the performance and yield of devices can be greatly improved.

In the present invention, as shown in FIG. 31, the optical latent imageforming zone is connected with the Al selective deposition zone throughthe gate valve so that the process can be continuously carried on. Thesame effect, can be obtained also when they are independentlyconstructed, though accompanied with a little increase in the number ofsteps.

FIG. 32 schematically illustrates the whole of the present apparatus,i.e., a vacuum through-processing apparatus. Reference numeral 721denotes a plasma film forming chamber in which an insulating film and asemiconductor film are formed by plasma deposition, that can bevacuum-sealed; 722, an etching chamber in which films are processed bychemical dry etching, that can be vacuum-sealed; 723, a cleaning chamberin which the surfaces of samples are cleaned using plasma, that can bevacuum-sealed; 724, a transport assembly for transporting the substrate701 to each processing chamber; and 725, a transport chamber that can bevacuum-sealed, provided with the transport assembly 724. Referencenumerals 704d, 704e, 704f and 704g each denote a gate valve throughwhich the substrate 701 can be put in and out, that can vacuum-seal eachchamber. Other components indicated by the same reference numerals asthose in FIG. 31 denote the same components.

Since, in general, the photolithography making use of a resit can not becarried out in vacuum, it has been hithertofore impossible to carry outin vacuum the whole process for fabricating a device. Application of theprocess according to the method of the present invention makes itpossible to carry out a vacuum through-processing.

This embodiment will be more specifically described below by givingexamples.

Example 19

An example will be described in which, using the apparatus as shown inFIG. 31, an Al electrode pattern is formed on a Si substrate 701 onwhich an n⁺ a-Si film (n⁺ amorphous silicon film) with a thickness of2,000 Å has been deposited.

First, the gate valve 704a was opened, and the Si substrate 701 was putin the load lock chamber 702. The gate valve 704a was closed, and thevacuum exhaust system 703a was operated to evacuate the inside of theload lock chamber 702 to a pressure of 10⁻⁷ Torr or less. The vacuumexhaust system 703b was operated to previously evacuate the inside ofthe latent image forming chamber 707 to a pressure of 10⁻⁸ Torr or less.The gate valve 704b was opened and the Si substrate 701 was placed onthe substrate holder 706b. O₂ gas was fed from the gas inlet 705b intothe latent image forming chamber 707, and the vacuum exhaust system 703bwas operated so as for the inside pressure to be adjusted to 20 Torr.Using an electron synchrotron as the light source 708a, light with awavelength of 160 nm to 260 nm was selected in the light control section708b, with which the mask 710 for forming the electrode pattern wasuniformly irradiated by means of the illumination optical system 709. Apattern image of the mask 715 was formed on the surface of the n⁺ a-Sifilm through the window 712 by means of the projection optical system711. As a material for the window, quartz was used. On the surface ofthe n⁺ a-Si film on which the mask image had been formed, O₂ and Sicaused photochemical reaction only at the part irradiated with thelight, and upon exposure for 10 minutes an SiO₂ layer with a thicknessof about 80 Å was formed on the n⁺ a-Si film surface. This reaction didnot proceed at the part not irradiated with the light. Hence, the Si wasconsequently converted to SiO₂ to form a latent image only in the regionirradiated with the light on the surface of the n⁺ a-Si film, and thus anon-electron-donative layer was formed there. In other words, this meansthat a negative pattern of the mask pattern was formed on the n⁺ a-Sifilm surface. After the formation of the latent image, the gas supplywas stopped, and the inside of the latent image forming chamber 707 wasevacuated to a pressure of 10⁻⁷ Torr or less. The vacuum exhaust system703c was operated to previously evacuate the inside of the Al selectivedeposition chamber 713 to a pressure of 10⁻⁷ Torr or less. The gatevalve 704c was opened and the Si substrate 701 was placed on thesubstrate holder 706c having been previously heated to 300° C. by meansof the heater 714 provided inside the Al selective deposition chamber713. The gate valve 704c was closed and the inside of the Al selectivedeposition chamber 713 was evacuated to a pressure of 10⁻⁸ T orr or lessby means of the vacuum exhaust system 703c. Using H₂ as a carrier gas,DMAH was supplied from a first gas line of the gas mixer 715, and H₂ wassupplied from a second gas line thereof. After the temperature of the Sisubstrate 701 reached 300° C., DMAH and H₂ were fed from the gas inlet705c into the Al selective deposition chamber 713. Then the gas mixer715 and the vacuum exhaust system 703c were operated so as for the totalpressure in the Al selective deposition chamber 713 and the partialpressure of DMAH to be adjusted to 1.5 Torr and 1.5×10⁻⁴ Torr,respectively. After deposition was carried out for 10 minutes, thesupply of DMAH was stopped, and then the heating with the heater 714 wasstopped to cool the Si substrate 701. The supply of H₂ was stopped, andthe inside of the Al selective deposition chamber 713 was evacuated to apressure of 10⁻⁷ Torr or less by operating the vacuum exhaust system703c. The gate valves 704c and 704b were opened, and the Si substrate701 was put in the load lock chamber 702. Then the gate valve 704b wasclosed, and N₂ gas was fed from the gas inlet 705a until the insidereached the atmospheric pressure. Then the gate valve 704a was opened totake out the Si substrate 701. As a result, No Al was deposited at allon the surface provided with the latent image, and also was notdetectable by surface analysis using Auger electron spectroscopy. On theother hand, on the surface of the a-Si film, an Al film with a goodquality, containing no carbon at all (below detection limit), having aresistivity of 2.7 μΩ·cm, an average wiring life time of 1×10³ to 10⁴hours and a hillock density of 0 to 10 in number/cm² and being free fromoccurrence of spikes, was selectively deposited to form the electrode.

Example 20

An example will be described in which, using the apparatus as shown inFIG. 31, an Al electrode pattern is formed on a GaAs substrate.

First, the gate valve 704a was opened, and a GaAs substrate 701 havingbeen previously cleaned was put in the load lock chamber 702. The gatevalve 704a was closed, and the vacuum exhaust system 703a was operatedto evacuate the inside of the load lock chamber 702 to a pressure of10⁻⁷ Torr or less. The vacuum exhaust system 703b was operated topreviously evacuate the inside of the latent image forming chamber 707to a pressure of 10⁻⁸ Torr or less. The gate valve 704b was opened andthe GaAs substrate 701 was placed on the substrate holder 706b. NO₂ gaswas fed from the gas inlet 705b into the latent image forming chamber707, and the vacuum exhaust system 703b was operated so as for theinside pressure to be adjusted to 20 Torr. Using an electron synchrotronas the light source 708a, light with a wavelength of 300 nm to 600 nmwas selected in the light control section 708b, with which the mask 710for forming the electrode pattern was uniformly irradiated by means ofthe illumination optical system 709. A pattern image of the mask 715 wasformed on the surface of the GaAs substrate 701 through the window 712by means of the projection optical system 711. As a material for thewindow, quartz was used. On the surface of the GaAs substrate 701irradiated with the light, NO₂ and Si caused photochemical reaction onlyat the part irradiated with the light, and an oxide film with athickness of about 100 Å was formed on the GaAs substrate 701 surface.After the formation of the latent image, the gas supply was stopped, andthe inside of the latent image forming chamber 707 was evacuated to apressure of 10⁻⁷ Torr or less. The vacuum exhaust system 703c wasoperated to previously evacuate the inside of the Al selectivedeposition chamber 713 to a pressure of 10⁻⁷ Torr or less. The gatevalve 704c was opened and the GaAs substrate 701 was placed on thesubstrate holder 706c having been previously heated to 300° C. by meansof the heater 714 provided inside the Al selective deposition chamber713. The gate valve 704c was closed and the inside of the Al selectivedeposition chamber 713 was evaluated to a pressure of 10⁻⁸ Torr by meansof the vacuum exhaust system 703c. Using H₂ as a carrier gas, DMAH wassupplied from a first gas line of the gas mixer 715, and H₂ was suppliedfrom a second gas line thereof. After the temperature of the GaAssubstrate 701 reached 300° C., DMAH and H₂ were fed from the gas inlet705c into the Al selective deposition chamber 713. Then the gas mixer715 and the vacuum exhaust system 703c were operated so that the totalpressure in the Al selective deposition chamber 713 and the partialpressure of DMAH is adjusted to 1.5 Torr and 1.5×10⁻⁴ Torr,respectively. After deposition was carried out for 10 minutes, thesupply of DMAH was stopped, and then the heating with the heater 714 wasstopped to cool the GaAs substrate 701. The supply of H₂ was stopped,and the inside of the Al selective deposition chamber 713 was evacuatedto a pressure of 10⁻⁷ Torr or less by operating the vacuum exhaustsystem 703c. The gate valves 704c and 704b were opened, and the GaAssubstrate 701 was put in the load lock chamber 702. Then the gate valve704b was closed, and N₂ gas was fed from the gas inlet 705a until theinside reached the atmospheric pressure. Then the gate valve 704a wasopened to take out the GaAs substrate 701. As a result, it was possibleto form an Al film with a good quality, like the Al film in Example 19.

Example 21

According to the method of the present invention, an amorphous siliconphotosensor was fabricated using the vacuum through-processing apparatusshown in FIG. 32. Its process will be described with reference to FIGS.33A to 33E that show a schematic process chart. The gate valve 704a wasopened, and a quartz substrate 701 having been previously cleaned wasput in the load lock chamber 702. The gate valve 704a was closed, andthe vacuum exhaust system 703a was operated to evacuate the inside ofthe load lock chamber 702 to a pressure of 10⁻⁷ Torr or less. The insideof the transport chamber 725 was previously evacuated to always keep thepressure to 10⁻⁷ Torr or less by means of a vacuum exhaust system (notshown). The gate valve 704g was opened and the sample quartz substrate701 was taken out of the load lock chamber 702 by means of the transportassembly 724. Then the gate valve 704f was opened, and the substrate 701was moved through the transport chamber 725 to the cleaning chamber 723previously evacuated to a pressure of 10⁻⁷ Torr or less by means of thevacuum exhaust system 703f, and placed on the substrate holder 706f.Then the gate valve 704f was closed. The vacuum exhaust system 703f wasoperated to evacuate the inside of the cleaning chamber 723 to apressure of 10⁻⁸ Torr or less. A gas (in this instance, Ar at a flowrate of 50 sccm) for cleaning the surface of the quartz substrate 701was led from the gas inlet 705f into the cleaning chamber 723, and anvacuum exhaust system (not shown) was operated so as for the pressure inthe cleaning chamber 723 to be adjusted to 0.08 Torr. Next, a currentwith a high frequency of 13.56 MHz and 100 W generated in thehigh-frequency power source was applied to the substrate holder whilemaking adjustment of the matching box, to generate plasma in the spacebetween the substrate holder and the counter electrode. Since thesubstrate holder was insulated by a capacitor in a direct-currentfashion, a negative DC bias voltage of about -60 kV was generated in thesubstrate holder 706f because of the difference in mobility betweenelectrons and ions. Because of this voltage, Ar ions were acceleratedand they collided against the surface of the the quartz substrate 701,so that the stain present on the surface was physically removed bysputtering and thus a cleaned surface was obtained. The processing timewas about 3 minutes. After completion of this processing, the gas supplywas stopped, and the inside of the cleaning chamber 723 was evacuated toa pressure of 10⁻⁷ Torr or less. The gate valve 704f was opened, and thequartz substrate 701 was taken out by means of the transport assembly724. Then the gate valve 704f was closed, and the inside of the cleaningchamber 723 was kept evacuated to a pressure of 10⁻⁷ Torr or less.

The vacuum exhaust system was operated to previously evacuate the insideof the plasma chamber 721 to a pressure of 10⁻⁷ Torr or less. The gatevalve 704d was opened. The quartz substrate 701 was led into the plasmafilm forming chamber 721, and placed on the substrate holder having beenpreviously heated to 350° C. by means of a heater. Then the gate valve704d was closed. The inside of the plasma film forming chamber 721 wasevaluated to a pressure of 10⁻⁷ Torr or less by means of the vacuumexhaust system, and the quartz substrate 701 was heated until itstemperature reached 350° C. SiH₄, H₂ and NH₃ were fed at flow rates of10 sccm, 100 sccm and 300 sccm, respectively, into the plasma filmforming chamber 721, and the vacuum exhaust system was operated so asfor the pressure in the plasma film forming chamber 721 to be adjustedto 0.2 Torr. A current with a high frequency of 13.56 MHz and 50 Wgenerated in the high-frequency power source was applied to the counterelectrode while making adjustment of the matching box, to generateplasma in the space between the substrate holder and the counterelectrode. The gases fed in were decomposed with the plasma to depositan amorphous silicon nitride (a-SiN) film 734 in a thickness of 1,000 Å(FIG. 33A). After the film was formed, the gas supply was stopped, andthe vacuum exhaust system was operated to evacuate the inside of theplasma film forming chamber 721 to a pressure of 10⁻⁷ Torr or less. Thenthe gate valve 704d was opened, and the quartz substrate 701 was takenout by means of the transport assembly 724. The gate valve 704d wasclosed, and the plasma film forming chamber 721 was evacuated so as forits inside pressure to be kept at 10⁻⁷ Torr or less.

Next, the latent image forming chamber 707 was previously evacuated to apressure of 10⁻⁷ Torr or less by means of the vacuum exhaust system703d. The gate valve 704b was opened. The quartz substrate 701 was ledinto the latent image forming chamber 707 by means of the transportassembly 724, and placed on the substrate holder 706b. Then the gatevalve 704b was closed. The vacuum exhaust system 703b was operated toevacuate the inside of the latent image forming chamber 707 to apressure of 10⁻⁷ Torr or less. In the same way as in Example 19, alatent image was formed on an a-SiN film 734. The gate valve 704b wasopened and the quartz substrate 701 was taken out by means of thetransport assembly 724. Then the gate valve 704b was closed, and thelatent image forming chamber 707 was evacuated so as for its insidepressure to be kept at 10⁻⁷ Torr or less. The vacuum exhaust system 703cwas operated to previously evacuate the inside of the Al selectivedeposition chamber 713 to a pressure of 10⁻⁷ Torr or less. The gatevalve 704c was opened. The quartz substrate 701 was led into the Alselective deposition chamber 713 by means of the transport assembly 724and was placed on the substrate holder 706c. Then the gate valve 704cwas closed. The vacuum exhaust system 703c was operated to evacuate theinside of the Al selective deposition chamber 713 to a pressure of 10⁻⁸Torr or less. In the same way as in Example 19, an Al lower electrode735 with a thickness of 3,000 Å was formed as shown in FIG. 33B. Thegate valve 704c was opened, and the quartz substrate 701 was taken outby means of the transport assembly 724. Then the gate valve 704c wasclosed. The Al selective deposition chamber 713 was evacuated so as forits inside pressure to be kept at 10⁻⁷ Torr or less.

Next, the gate valve 704d was opened. The quartz substrate 701 was ledinto the plasma film forming chamber 721 by means of the transportassembly 724, and was placed on the substrate holder previously heatedto 350° C. with a heater. Then the gate valve 704d was closed. Theinside of the plasma film forming chamber 721 was evaluated to apressure of 10⁻⁷ Torr or less by means of the vacuum exhaust system, andthe quartz substrate 701 was heated until its temperature reached 350°C. SiH₄, H₂ and NH₃ were fed at flow rates of 10 sccm, 100 sccm and 300sccm, respectively, from the gas inlet into the plasma film formingchamber 721, and the vacuum exhaust system was operated so as for thepressure in the plasma film forming chamber 721 to be adjusted to 0.2Torr. A current with a high frequency of 13.56 MHz and 50 W generated inthe high-frequency power source was applied to the counter electrodewhile making adjustment of the matching box, to generate plasma in thespace between the substrate holder and the counter electrode. The gasesfed in were decomposed with the plasma to deposit an amorphous siliconnitride (a-SiN) film 736 in a thickness of 3,000 Å as shown in FIG. 33C.After the film was formed, the gas supply was stopped, and the vacuumexhaust system 703d was operated to evacuate the inside of the plasmafilm forming chamber 721 to a pressure of 10⁻⁷ Torr or less. Then thetemperature of the substrate holder 706 was dropped to 250° C. to setthe temperature of the quartz substrate 701 to 200° C. SiH₄ and H₂ werefed at flow rates of 60 sccm and 600 sccm, respectively, into the plasmafilm forming chamber 721, and the vacuum exhaust system was operated soas for the pressure in the plasma film forming chamber 721 to beadjusted to 0.5 Torr. A current with a high frequency of 13.56 MHz and60 W generated in the high-frequency power source was applied to thecounter electrode while making adjustment of the matching box, togenerate plasma in the space between the substrate holder and thecounter electrode. The gases fed in were decomposed with the plasma todeposit an amorphous silicon (a-Si) film 737 in a thickness of 1.5 μm asshown in FIG. 33C. After the film was formed, the gas supply wasstopped, and the inside of the plasma film forming chamber 721 wasevacuated to a pressure of 10⁻⁷ Torr or less. Next, SiH₄, H₂ and H₂-diluted 100 ppm PH₃ were fed at flow rates of 3 sccm, 30 sccm and 400sccm, respectively, into the plasma film forming chamber 721, and thevacuum exhaust system was operated so as for the pressure in the plasmafilm forming chamber 721 to be adjusted to 0.5 Torr. A current with ahigh frequency of 13.56 MHz and 300 W generated in the high-frequencypower source was applied to the counter electrode while makingadjustment of the matching box, to generate plasma in the space betweenthe substrate holder and the counter electrode. The gases fed in weredecomposed with the plasma to deposit an n⁺ a-Si film 738 in a thicknessof 2,000 Å as shown in FIG. 33C. After the film was formed, the gassupply was stopped, and the vacuum exhaust system was operated toevacuate the inside of the plasma film forming chamber 721 to a pressureof 10⁻⁷ Torr or less.

Next, the gate valve 704b was opened. The quartz substrate 701 was ledinto the latent image forming chamber 707 by means of the transportassembly 724, and was placed on the substrate holder 706b. Then the gatevalve 704b was closed. The inside of the latent image forming chamber707 was evacuated to a pressure of 10⁻⁷ Torr or less by means of thevacuum exhaust system 703b. In the same way as in Example 19, a latentimage was formed on the n⁺ a-Si film 738. The gate valve 704b was openedand the quartz substrate 701 was taken out by means of the transportassembly 724. Then the gate valve 704b was closed, and the latent imageforming chamber 707 was evacuated so as for its inside pressure to bekept at 10⁻⁷ Torr or less. The vacuum exhaust system 703c was operatedto previously evacuate the inside of the Al selective deposition chamber713 to a pressure of 10⁻⁷ Torr or less. The gate valve 704c was opened.The quartz substrate 701 was led into the Al selective depositionchamber 713 by means of the transport assembly 724 and was placed on thesubstrate holder 706c. Then the gate valve 704c was closed. The vacuumexhaust system 703c was operated to evacuate the inside of the Alselective deposition chamber 713 to a pressure of 10⁻⁸ Torr or less. Inthe same way as in Example 19, an Al upper electrode 739 with athickness of 6,000 Å was formed as shown in FIG. 33D. The gate valve704c was opened, and the quartz substrate 701 was taken out by means ofthe transport assembly 724. Then the gate valve 704c was closed. The Alselective deposition chamber 713 was evacuated so as for its insidepressure to be kept at 10⁻⁷ Torr or less.

Next, the vacuum exhaust system was operated to previously evacuate theinside of the etching chamber 722 to a pressure of 10⁻⁷ Torr or less,and the gate valve 704e was opened. The quartz substrate 701 was ledinto the etching chamber 722 by means of the transport assembly 724, andwas placed on the substrate holder. Then the gate valve 704e was closed.The vacuum exhaust system was operated to evacuated the inside of theetching chamber 722 to a pressure of 10⁻⁷ Torr or less. As etchinggases, NF₃, O₂ and H₂ were fed at flow rates of 700 sccm, 200 sccm and100 sccm, respectively, from the gas inlet into the microwave plasma gasexciting device, and the vacuum exhaust system was operated so as forthe inside of the etching chamber 722 to be adjusted to 0.25 Torr.Microwaves of 2.45 GHz and 700 W generated in a microwave generator weresupplied to the microwave plasma gas exciting device, and the etchinggas was made to plasma. Only neutral radicals excited by this plasmawere transported to the etching chamber 722 through the transport pipe.Using the Al upper electrode 739 as a mask, the latent image of theoxide film formed on the n⁺ a-Si film 738 was first etched. Next, NF₃and O₂ were flowed as etching gases at flow rates of 800 sccm and 200sccm, respectively, and as shown in FIG. 33D the n⁺ a-Si film 738 wasetched to form a light incidence opening 740. After the etching wascompleted, the etching gas was stopped, and the vacuum exhaust system703e was operated to evacuate the inside of the etching chamber 722 to apressure of 10⁻⁷ Torr or less. Then the gate valve 704e was opened, andthe quartz substrate 701 was taken out by means of the transportassembly 724. The gate valve 704e was closed, and the inside of theetching chamber 722 was evacuated so as to be kept to a pressure of 10⁻⁷Torr or less.

Next, the gate valve 704d was opened. The quartz substrate 701 was ledinto the plasma film forming chamber 721 by means of the transportassembly 724, and was placed on the substrate holder previously heatedto 350° C. with a heater. Then the gate valve 704d was closed. Theinside of the plasma film forming chamber 721 was evacuated to apressure of 10⁻⁷ Torr or less by means of the vacuum exhaust system, andthe quartz substrate 701 was heated until its temperature reached 350°C. SiH₄, H₂ and NH₃ were fed at flow rates of 10 sccm, 100 sccm and 300sccm, respectively, from the gas inlet into the plasma film formingchamber 721, and the vacuum exhaust system was operated so as for thepressure in the plasma film forming chamber 721 to be adjusted to 0.2Torr. A current with a high frequency of 13.56 MHz and 80 W generated inthe high-frequency power source was applied to the counter electrodewhile making adjustment of the matching box, to generate plasma in thespace between the substrate holder and the counter electrode. The gasesfed in were decomposed with the plasma to deposit an amorphous siliconnitride (a-SiN) film 741 in a thickness of 2 μm (FIG. 33E). After thefilm was formed, the gas supply was stopped, and the vacuum exhaustsystem was operated to evacuate the inside of the plasma film formingchamber 721 to a pressure of 10⁻⁷ Torr or less. The gate valve 704e wasopened, and the quartz substrate 701 was taken out by means of thetransport assembly 724. The inside of the plasma film forming chamber721 was evacuated so as for its inside pressure to be kept to 10⁻⁷ Torror less.

The gate valve 704g was opened, and the quartz substrate 701 was put inthe load lock chamber 702 by means of the transport assembly 724. Thenthe gate valve 704g was closed. N₂ gas was fed into the load lockchamber 702 so that the pressure in the chamber was returned to theatmospheric pressure, and then the quartz substrate 701 on which theamorphous silicon photosensor had been fabricated was taken out.Measurement of the performance of the amorphous silicon photosensor thusfabricated in the present example revealed that it had a low internalresistance, a high sensitivity and a less dark current.

The example described above shows the instance in which the selectivelydepositing metal is aluminum. Without limitation thereto, in the presentinvention, a metal compound mainly composed of aluminum as exemplifiedby aluminum silicon that is deposited by reacting DMAH with asilicon-containing gas and hydrogen may also be used as the selectivelydepositing metal.

Example 22

A still further embodiment of the present invention will be describedbelow with reference to the drawings.

FIG. 34 illustrates an example of an apparatus for fine-processing asemiconductor device according to the present invention.

The fine-processing apparatus of the present example comprises avacuum-sealed cleaning chamber 801 in which a sample 803 is cleaned, alatent image forming chamber 808 in which the surface of the sample 803is modified to form a patterned latent image, and an etching chamber 818in which the sample 803 is etched.

The cleaning chamber 801 is provided with i) a sample holder 802a onwhich the sample 803 is placed through a gate valve 807a, and ii) amicrowave gas exciting device 804a in which a cleaning gas fed in from acleaning gas inlet 805 is excited using microwaves generated in amicrowave generator (not shown) and from which the gas thus excited issupplied to the cleaning chamber 801 through a transport pipe 806a(total length: 20 cm; inner diameter: 40 mm) made of alumina.

The latent image forming chamber 808 is provided with i) a sample holder802b on which the sample 803 transferred from the cleaning chamber 801through a gate valve 807b without its exposure to the atmosphere isplaced and which has a temperature control mechanism described later,ii) latent image forming gas inlets 805b and 805c from which a latentimage forming gas serving as a modifying gas is fed in, and iii) amicrowave gas exciting device 804b that excites the latent image forminggas fed in from the latent image forming gas inlet 805b and supplies theexcited gas to the latent image forming chamber 808 through a transportpipe 806b (total length: 20 cm; inner diameter: 40 mm) made of alumina.This chamber 808 is also constituted in such a way that a mask 815 (or areticle) comprising a quartz plate patterned with Cr is uniformelyirradiated with light of a KrF excimer laser 813 serving as a lightsource, through an illumination optical system 814, and a patternedlatent image of the mask 815 is formed on the surface of the sample 803placed on the sample holder 802b, through a projection optical system816 and a transmission window 817.

The temperature control mechanism provided in the above sample holder802b is provided with a refrigerant reservoir 809 in which a refrigerantfor cooling the sample 803 placed on the sample holder 802b is stored,and a heater 812 that heats the sample 803. The refrigerant reservoir809 is constituted in such a way that the refrigerant is supplied from arefrigerant feed inlet communicating with the refrigerant reservoir 809and the refrigerant having been evaporated in the refrigerant reservoir809 is discharged outside through a gas vent pipe 811 similarlycommunicating with the refrigerant reservoir 809.

The etching chamber 818 is provided with a sample holder 802c on whichthe sample 803 transferred from the latent image forming chamber 808through a gate valve 807c without its exposure to the atmosphere isplaced, and is also provided above the sample holder with a plasmachamber 819 in which plasma for etching is generated, and a magneticcoil 821 for producing a magnetic field in the plasma chamber 819.

In the plasma chamber 819, the plasma for etching is generated by themicrowave supplied from the microwave generator (not shown) through themicrowave transmission window 820, the etching gas fed in from theetching gas inlet 805d and the magnetic field produced by the magneticcoil 821. This plasma chamber 819 and the above magnetic coil 821 are soconstituted that they can be cooled with cooling water fed in from acooling water inlet 822 and flowed out to the cooling water outlet 823.

The fine-processing apparatus used in the present example is alsoprovided with vacuum exhaust systems (not shown) that can evacuate therespective cleaning chamber 801, latent image forming chamber 808 andetching chamber 818 to set their insides to a given pressure.

An instance will be described below in which a sample 803 comprising anSi substrate, an SiO₂ film formed thereon with a thickness of 200 Å andan n⁺ poly-Si film formed thereon with a thickness of 3,000 Å isfine-processed using the fine-processing apparatus as described above.

First, the sample 803, Si substrate was transported through the gatevalve 807a to the inside of the cleaning chamber 801, and placed on thesample holder 802a. The vacuum exhaust system was operated to previouslyevacuate the inside of the cleaning chamber 801 to a pressure of 10⁻⁸Torr or less. From the cleaning gas inlet 805a, a cleaning gas (NF₃ ;500 sccm) for cleaning the surface of the sample 803 was fed into themicrowave gas exciting device 804a, and then the vacuum exhaust systemwas operated for the pressure in the cleaning chamber 801 to be adjustedto 0.25 Torr. Microwaves of 2.45 GHz and 700 W generated in themicrowave generator were also supplied to the microwave gas excitingdevice 804a to excite the cleaning gas already fed into the microwavegas exciting device 804a. Active species thereby produced, i.e., excitedmolecules NF₃ ⁺, NF₂ ⁺, NF⁺ and F⁺, were supplied to the cleaningchamber 801 through the transport pipe 806a. In the cleaning chamber801, the above excited molecules having reached the sample 803, Sisubstrate, and natural oxide film (SiO₂) formed on the surface of the n⁺poly-Si film reacted with each other to produce a silicon fluoridecompound, a volatile substance, so that the natural oxide film (SiO₂)formed on the surface of the n⁺ poly-Si film was removed to give a cleansurface. This processing was completed in about 20 seconds. After theprocessing was completed, the supply of the cleaning gas was stopped,and the vacuum exhaust system was operated to evacuate the inside of thecleaning chamber 801 to a pressure of 10⁻⁸ Torr or less.

Next, the latent image forming chamber 808 was previously evacuated to apressure of 10⁻⁸ Torr or less by means of the vacuum exhaust system. Thegate valve 807b was opened and the sample 803, Si substrate, was movedfrom the cleaning chamber 801 to 1the latent image forming chamber 808,and was placed on the sample holder 802b. After the gate valve 807b wasclosed, the latent image forming chamber 808 was again evacuated to apressure of 10⁻⁸ Torr or less. Then, a latent image forming gas NO₂ wasfed from the latent image forming gas inlet 805c into the latent imageforming chamber 808, and the vacuum exhaust system was operated so asfor the inside pressure to be adjusted to 1 Torr. Since the temperatureat which the saturated vapor pressure of NO₂ gas came to be 1 Torr was-50° C., liquefied nitrogen serving as the refrigerant was supplied tothe refrigerant reservoir 809, and the temperature of the sample holder802b was controlled while adjusting the heater 812, to set thetemperature of the sample 803, Si substrate, to -50° C.±10° C. Then theNO₂ gas was brought into contact for 80 seconds with the n⁺ poly-Si filmformed on the Si substrate. In such a state, the NO₂ gave a balancedvaporizing and solidifying state on the surface of the n⁺ poly-Si film,and hence the NO₂ was absorbed to the n⁺ poly-Si film surface in a goodefficiency.

Next, the mask 815 to which the desired pattern had been applied bymeans of the illumination optical system 814 was uniformly irradiatedwith laser light with a wavelength of 248 nm radiated from the KrFexcimer laser 813, and also a pattern image of the mask 815 was formedon the surface of the sample 803 by means of the projection opticalsystem 816 through the transmission window 817. As a material for thetransmission window 817, a quartz plate was used so that the laser lightwith a wavelength of 248 nm was transmitted without being absorbedtherein.

In regard to the sample 803, absorbed NO₂ and Si caused photochemicalreaction only at the part irradiated with the light on its n⁺ poly-Sifilm surface on which the pattern images had been formed, and, uponexposure for 2 minutes, an SiO₂ film with a thickness of about 30 Å wasformed on the n⁺ poly-Si film. Since this reaction did not proceed atthe part not irradiated with the light, a negative pattern of this maskwas consequently formed on the n⁺ poly-Si film. In other words, the n⁺poly-Si was modified to SiO₂ to form the latent image. Since thisreaction took place only at the part irradiated with the light, the NO₂molecules adsorbed to the surface inhibit the reaction of excitedmolecules with the Si surface even when the excited molecules producedas a result of excitation and decomposition of NO₂ in the gaseous phasebecause of the irradiation light have reached the n⁺ poly-Si filmsurface. Hence the image pattern formed on the n⁺ poly-Si film surfacewas by no means blurred.

Subsequently, the sample 803 comprising the n⁺ poly-Si film on thesurface of which the SiO₂ film was formed to have the desired pattern,was heated with the heater 812 to 150° C. to release the NO₂ moleculesadsorbed to the n⁺ poly-Si film surface. Then the inside of the latentimage forming chamber 808 was evacuated to a pressure of 10⁻⁸ Torr orless.

Next, the vacuum exhaust system was operated to previously evacuate theetching chamber 818 and plasma chamber 819 provided above the etchingchamber 818, to a pressure of 10⁻⁸ Torr or less, and then the gate valve807c was opened. The sample 803 was moved from the latent image formingchamber 808 to the etching chamber 818, and was placed on the sampleholder 802c. After the gate valve 807c was closed, the etching chamber818 was again evacuated to a pressure of 10⁻⁸ Torr or less. Then, fromthe etching gas inlet 805d, Cl₂ was fed as an etching gas at a flow rateof 200 sccm into the plasma chamber 819, and the vacuum exhaust systemwas operated so as for the inside pressure to be adjusted to 3×10⁻⁴Torr. Cooling water was also fed in from the cooling water inlet 822,and the magnetic coil 821 was electrified while cooling the magneticcoil 821 and the plasma chamber 819, to produce a magnetic field in theplasma chamber 819. Microwaves of 2.45 GHz and 300 W generated in themicrowave generator were also guided through the wave guide and suppliedto the plasma chamber 819 through the microwave transmission window 822.In the plasma chamber 819, the electric field of the microwaves and themagnetic field produced by the magnetic coil accelerated electrons in agood efficiency to cause ionization of neutrons, so that dense argonplasma was generated. Here, the plasma was generated in a betterefficiency when the size of the magnetic field generated in the plasmachamber 819 was kept to the size of a magnetic field that causedelectronic cyclotron resonance (875 Gauss in the case of 2.45 GHzmicrowaves). The plasma generated in the plasma chamber 819 was spreadfrom the plasma chamber 819 into the etching chamber 818 along themagnetic line of force, and reached the surface of the sample 803. Withthis plasma, the uncovered n⁺ poly-Si film was etched for 3 minutesusing as a protective film the SiO₂ film formed in the latent imageforming chamber 808. Since the ratio in etching rate, i.e., selectionratio, of n⁺ poly-Si to SiO₂ resulted in about 120, it was possible toetch the n⁺ poly-Si layer without disappearance of the SiO₂ layer. Sincethe gas pressure was as low as 3×10⁻⁴ Torr, ions reached the n⁺ poly-Sifilm surface without their bombardment with other particles, so that itwas possible to carry out etching in a good anisotropy. Since also theion energy was 10 or so eV, it was possible to carry out etching withless damage.

When the SiO₂ layer serving as the protective layer was formed withoutcooling the sample 803, Si substrate, in the course of the latent imageformation in the latent image forming chamber 808, the SiO₂ layer cameto have a thickness of 10 Å or less. Thus, in order to etch the n⁺poly-Si layer without disappearance of the SiO₂ layer, the selectivityratio was required to be 300 or more, and it was actually impossible todo so.

In the present example, the cleaning of the sample 803, carried out inthe cleaning chamber 801, was effected by exciting microwaves using themicrowave gas exciting device 804a. It was also possible to carry out itusing plasma.

FIG. 35 illustrates the constitution of a cleaning chamber 801a usedwhen the sample 803 is cleaned using plasma.

The cleaning chamber 801a shown in FIG. 35 comprises a cleaning gasinlet 805e from which a cleaning gas is fed into the chamber. In itsinside, a counter electrode 827 is provided opposingly to a sampleholder 802a. A high-frequency power source 825 that applies ahigh-frequency current to the sample holder 802a is also equipped via amatching box. The sample holder 802a is also provided with an insulator824 that insulates the matching box 826 and the high-frequency powersource 825 in the direction of direct currents. In FIG. 35, the samecomponents as those of the cleaning chamber 801 shown in FIG. 34 aredenoted by the same reference numerals.

In this example, a vacuum exhaust system (not shown) was operated tokeep the inside of the cleaning chamber 801a evacuated to a pressure of10⁻⁸ Torr or less, and the above sample 803 was placed on the sampleholder 802a through the gate valve 807a. Then the cleaning gas (Ar; 50sccm) for cleaning the surface of the sample 803 was fed from thecleaning gas inlet 805e into the cleaning chamber 801a, and the vacuumexhaust system was operated so as for the pressure in the chamber to beadjusted to 0.08 Torr. Next, a high-frequency current of 13.56 MHz and100 W was applied from the high-frequency power source 825 to the sampleholder 802a while controlling the matching box 826, to generate plasmain the space between the sample holder 802a and the counter electrode827. Since the sample holder 802a was insulated in the direction ofdirect currents, a negative DC bias voltage of about -60 kV wasgenerated at the sample holder 802a because of the difference inmobility between electrons and ions. Because of this voltage, Ar ionswere accelerated and they collided against the surface of the n⁺ poly-Sifilm, so that the stain and natural oxide film present on the surfacewere physically removed by sputtering and thus a cleaned surface wasobtained. The processing time was about 60 seconds. After thisprocessing was completed, the supply of the cleaning gas was stopped,and the inside of the cleaning chamber 801a was evacuated to a pressureof 10⁻⁸ or less. This step was followed by the same procedure aspreviously described, so that it was possible to form the latent imageand carry out the etching.

In the latent image forming chamber 808 of the present example, NO₂ wasused as the latent image forming gas. It was also possible to useexcited ozone as the latent image forming gas.

The instance where the ozone was used as the latent image forming gaswill be described below.

First, oxygen gas was fed from a latent image forming gas inlet 805bthrough the microwave gas exciting device 804b into the latent imageforming chamber 808, and a vacuum exhaust system (not shown) wasoperated so as for the pressure in the latent image forming chamber 808to be adjusted to 1 Torr. Since the temperature at which the saturatedvapor pressure of ozone came to be 1 Torr was -170° C., liquefiednitrogen serving as the refrigerant was supplied to the refrigerantreservoir 809, and the temperature of the sample holder 802b wascontrolled while adjusting the heater 812, to set the temperature of thesample 803 Si substrate to -170° C. ±10° C. Next, microwaves weresupplied to the microwave gas exciting device 804b to generate oxygenplasma, thereby exciting the ozone. The ozone thus excited was fed tothe latent image forming chamber 808 through the transport pipe 806b andadsorbed for 80 seconds on the surface of the n⁺ poly-Si film formed onthe Si substrate. Since at an ultra-low temperature of about -170° C.the ozone gave a balanced vaporizing and solidifying state on thesurface of the n⁺ poly-Si film, the ozone was absorbed to the n⁺ poly-Sifilm surface in a good efficiency. Since the saturated vapor pressure ofoxygen at this temperature was 1,500 mmHg, the amount of adsorption wassmaller than that of ozone and hence the adsorbed substance wascomprised of ozone in a greater part.

Thereafter, in the same way as previously described, a pattern image ofthe mask 815 was formed on the surface of the sample 803 using the lightfrom the KrF excimer laser 813, so that it was possible to form an SiO₂layer after the pattern image.

In the latent image forming chamber 808 described above, a KrF excimerlaser was used as the light source. It was also possible to obtain thesame effect using a lamp light source such as a xenon lamp or ahigh-pressure mercury lamp, or an ultraviolet laser such as an ArFexcimer laser, an XeCl excimer layer or an Ar⁺ laser.

In regard to the etching chamber 818 described above, an example wasshown in which etching completely free from damage was carried out usingmicrowave plasma. As another example thereof, it was also possible touse chemical dry etching although it was considered probable that itsfine-processing performance was poorer than the case the microwaveplasma was used.

FIG. 36 illustrates the constitution of an etching chamber 818a in thecase when the chemical dry etching was used.

This etching chamber 818a is equipped with a microwave gas excitingdevice 804c that excites an etching gas fed in the chamber from anetching gas inlet 805f, by means of a microwave generator (not shown).The etching gas excited using the microwave gas exciting device 804c issupplied into the etching chamber 818a through a transport pipe 806c(total length: 20 cm; inner diameter: 40 mm) made of alumina. As toother constitution, the same components as those in FIG. 34 are denotedby the same reference numerals.

In the case when the etching is carried out using this etching chamber818a, a vacuum exhaust system (not shown) was operated to previouslyevacuate the inside of the etching chamber 818a to a pressure of 10⁻⁸Torr or less. Then the gate valve 807c was opened, and, in the same wayas previously described, the sample 803 comprising an Si substratehaving an n⁺ poly-Si film on which the desired pattern had been applied(i.e., the SiO₂ film) was placed on a sample holder 802c provided in theetching chamber 818a. After the gate valve 807c was closed, the etchingchamber 818a was again evacuated to a pressure of 10⁻⁸ Torr or less.Then an etching gas (Cl₂ ; 500 sccm) was fed from the etching gas inlet805f into the microwave gas exciting device 804c and at the same timethe vacuum exhaust system was operated so as for the pressure in theetching chamber 818a to be adjusted to 0.25 Torr.

In this state, microwaves of 2.45 GHz and 700 W generated in themicrowave generator were supplied to the microwave gas exciting device804c to excite the etching gas (Cl₂ ; 500 sccm) already fed from theetching gas inlet 805f into the chamber. Excited molecules Cl₂ ⁺ and Cl⁺were supplied to the etching chamber 818a through the transport pipe806c. At this time, the excited molecules Cl₂ ⁺ and Cl⁺ having reachedthe Si substrate reacted with the n⁺ poly-Si masked with the latentimage patterned SiO₂ layer formed on the surface of the n⁺ poly-Si film,so that a silicon chloride compound, a volatile substance, was producedand the n⁺ poly-Si layer was etched after the desired latent imagepattern.

As the method for the selective irradiation with light in the latentimage forming chamber, besides the method making use of the mask as inthe method shown in FIG. 34, it was also possible to effect theselective irradiation by a direct drawing method making use of laserlight shown in FIG. 37.

FIG. 37 illustrates a latent image forming chamber of the direct drawingtype making use of laser light. In the drawing, reference numeral 808adenotes a latent image forming chamber; 813a, an Ar⁺ ion laser servingas a light source; 828, an optical modulator; and 829, a collimaterlens. Reference numeral 830 denotes a rotary polyhedral mirror; 831, anf-θ lens; 832, an X stage that can move a sample holder 802b in thelaser-light scanning direction and the vertical direction. Othercomponents indicated by the same reference numerals as those shown inFIG. 34 denote the same components.

An example will be shown below in which a latent image is formed on thesample 803 Si substrate in the same way as in the example previouslydescribed, by the use of the direct drawing method.

Similar to the case previously described, the n⁺ poly-Si surface of thesample 803 was cleaned, and the sample 803 was placed on the sampleholder 802b in the latent image forming chamber 808 having been alreadyevacuated to a pressure of 10⁻⁸ Torr or less. Subsequently, a latentimage forming gas NO₂ was fed into the chamber, and the sample 803 wascooled. Next, laser light radiated from a light source Ar⁺ ion laser813a was so modulated in the optical modulator 828 as to enableformation of the desired pattern, and scanned in the unidimensionaldirection by means of the collimater lens and the polyhedral mirror 830.Thereafter, an image was formed on the surface of the sample 803 throughthe f-θ lens and the transmission window 817. The sample holder 802b wasalso moved using the X stage 832 in the laser-light scanning directionand the vertical direction, whereby it was possible to irradiate thewhole sample surface with the light. Any lasers can be used as the lightsource laser so long as they can cause photochemical reaction on thesurface. The light source used in forming the latent image of the oxidefilm on a GaAs substrate may include, besides the lasers previouslydescribed, an Ar laser, a krypton laser and a He--Cd laser.

At the part of the n⁺ poly-Si surface irradiated with light in the aboveway, photochemical reaction with absorbed NO₂ took place to form alatent image comprised of SiO₂. Thereafter, it was possible to carry outetching in the same way as in the example previously described.

Example 23

Another example of the present invention will be described below givingan example in which an Al electrode pattern is formed on a quartzsubstrate.

First, on a quartz substrate as the sample 803, Al was deposited bysputtering in a thickness of 1,500 Å. The surface of the Al film of thesample 803 was cleaned with Ar ions using the aforesaid cleaning chamber801a as shown in FIG. 35.

Subsequently, the sample 803 thus cleaned was moved to the latent imageforming chamber 808 and was placed on the sample holder 802b in the sameway as in the example previously described. Then, ammonia gas NH₃ wasfed from the latent image forming gas inlet 805c into the latent imageforming chamber 808, and the vacuum exhaust system (not shown) wasoperated so as for the pressure in the inside to be adjusted to 1 Torr.Here, since the temperature at which the saturated vapor pressure of NH₃gas came to be 1 Torr was -103° C., liquefied nitrogen serving as therefrigerant was supplied to the refrigerant reservoir 809, and thetemperature of the sample holder 802b was controlled while adjusting theheater 812, to set the temperature of the sample 803 to -103° C.±10° C.Then NH₃ was adsorbed for 100 seconds on the Al film surface of thesample 803. Next, the mask 815 to which the desired patterning had beenapplied by means of the illumination optical system 814 was uniformlyirradiated with laser light with a wavelength of 248 nm radiated fromthe KrF excimer laser 813, and the resulting pattern image was formed onthe Al film surface of the sample 803 through the transmission window817 by means of the projection optical system 816. On the surface onwhich the pattern image was thus formed, adsorbed NH₃ and Al causedphotochemical reaction only at the part irradiated with the light, andupon exposure for 2 minutes an AlN film with a thickness of about 50 μmwas formed on the Al film surface. Since this reaction did not proceedat the part not irradiated with the light, a negative pattern of thismask was consequently formed on the Al film surface of the sample 803.

The sample 803 comprising the Al film on the surface of which the AlNlayer was formed to have the desired pattern, was heated with the heater812 to 150° C. for 3 minutes to release the molecules adsorbed to the Alfilm surface. Then the inside of the latent image forming chamber 808was evacuated to a pressure of 10⁻⁸ Torr or less.

Next, the vacuum exhaust system (not shown) was operated to previouslyevacuate the etching chamber 818 and plasma chamber 819 as shown in FIG.34 previously set out, to a pressure of 10⁻⁸ Torr or less, and the gatevalve 807c was opened. The sample 803 was moved from the latent imageforming chamber 808 to the etching chamber 818, and was placed on thesample holder 802c. After the gate valve 807c was closed, the etchingchamber 818 was again evacuated to a pressure of 10⁻⁸ Torr or less.Then, from the etching gas inlet 805d, an etching gas (Cl₂ ; 20 sccm)was fed into the plasma chamber 819, and the vacuum exhaust system wasoperated so as for the inside pressure to be adjusted to 3×10⁻⁴ Torr. Inthis state, a magnetic field of 875 Gauss was produced in the plasmachamber 819 by means of the magnetic coil 821 and at the same timemicrowaves of 2.45 GHz and 300 W were supplied from a microwavegenerator (not shown) to the plasma chamber 819 to produce plasma. Thenthe plasma thus produced was supplied onto the sample 803 put in theetching chamber 818 to carry out etching for 90 seconds. As a result, itwas possible to form on the sample 803 quartz substrate, an Al electrodewith a negative pattern of the mask 815.

The present invention, which is constituted as described above has thefollowing effects.

That is, in the processing method of the present invention, the physicaldamage is previously given to the film before the third step of formingthe mask pattern, whereby the mask pattern can be made thick and also adense device structure can be obtained. This brings about an improvementin etching inhibitory power and hence can improve fine-processingperformance in the photoetching. In addition, since the process can besimplified, devices can be fabricated rapidly.

It is also possible to prevent deterioration of devices and adhesion ofdust, and hence the yield can also be improved in addition to the aboveeffect.

Formation of a plurality of protective films can bring about asufficiently large total layer thickness, and hence the fine processingwith a sufficient etching depth can be applied.

The annealing of the surface-modified layer serving as a protective film(a mask) in etching makes it possible to form a protective film madestabler and stronger, and having a higher etching resistance. As aresult, it becomes possible to obtain the desired amount (depth) ofetching of the film to which the fine processing should be applied.

Needless to say, the same effect can also be obtained when the annealingis carried out using electron rays or lamps.

The heating of the film to which surface modification is applied, in thestep of forming the surface-modified layer, accelerates photochemicalreaction on the surface irradiated with light, and hence thesurface-modified layer can have a chemically stronger bond and also havea larger thickness. This can achieve i) an improvement in etchingresistance of the surface-modified layer and ii) an increase indifference in electron donative properties between the surface-modifiedlayer and the surface-unmodified layer. This enables pattern formationwith ease.

According to the present invention, the simultaneous irradiation on thesubstrate with the light that causes vibration of the moleculesconstituting the surface of the substrate and the light that causes thephotochemical reaction accelerates the reaction of the surface with thereactive gas. This makes it possible to process the substrate at a highrate. Since the photochemical reaction can be made to selectively takeplace on the surface irradiated with the processing light, it is alsopossible to carry out the desired processing in a good selectivity.

In the step of forming the surface-modified layer, use of the light, asthe processing light, that has an energy greater than a binding energyof the compound constituting the substrate surface and is capable ofreducing the compound makes it possible to selectively reducesemiconductors or metal compounds that are usually reduced only withdifficulty, to form the surface-modified layer. Carrying out the etchingusing the surface-modified layer as a mask makes it possible to carryout high-speed processing and yet to obtain a nice etched surface. Sincethe irradiation with light is effected in a high vacuum, it is possibleto prevent contamination of the light irradiation window.

The optical latent image film is formed using a synchrotron orbitradiation to cause a change in the electron donative properties on thesurface, so that the electrode or wiring comprising Al or a metal mainlycomposed of Al can be selectively formed. Since no resist is used, theprocess can be simplified and the dust is less produced, resulting in animprovement in yield, and metal films with a good quality can be formed.It is also possible to carry out vacuum through-processing ofsemiconductor devices, without exposure to the atmosphere, and hencesemiconductor devices with a high performance can be obtained. Since noAl etching step is required, no after-corrosion occurs, bringing aboutan improvement in the reliability of devices.

The present invention can also be effective on the following:

(1) In the latent image forming chamber, the temperature of thesubstrate is so controlled that the pressure of the modifying gasreaches the saturated vapor pressure, whereby the modifying gasmolecules can be adsorbed on the substrate surface in a good efficiency.Hence, the surface-modified layer formed on the substrate surface can bemade thick to bring about a high effect of protection when etching iscarried out.

(2) When surface-modified layer is formed on the substrate surface afterthe pattern of a circuit, the modifying gas molecules adsorbed on thesubstrate inhibit the substrate surface from reacting with the modifyinggas molecules present in an excited state, even in the case where themodifying gas molecules in an excited state generated as a result of thegaseous phase reaction of light with the modifying gas have reached thesubstrate surface having been not irradiated with the light. Hence, thesurface-modified layer formed after the circuit pattern is no longerblurred, and it becomes possible to carry out fine processing at ahigh-speed and accuracy.

(3) According to the apparatus for fine-processing semiconductordevices, the substrate can be moved from the latent image formingchamber to the etching chamber through the gate valve. Hence, no dustcan be adhered to the substrate surface, and the accuracy in the patternformation can be improved. In addition, the latent image forming chamberis connected with the cleaning chamber similarly through the gate valve,so that the substrate is cleaned before the surface-modified layer isformed on the substrate. This can bring about a great effect.

Needless to say, the respective processing methods and apparatusdescribed giving examples can be used in combination within the purportof the present invention, and also can be modified within the purport ofthe present invention.

We claim:
 1. A processing method comprising the steps of:subjecting asurface of a substrate to selective irradiation with a light in a gasatmosphere comprising oxygen or nitrogen to cause a photochemicalmodification of the surface of the substrate to form a surface-modifiedlayer; subjecting the surface of the substrate having thesurface-modified layer formed thereon to annealing to stabilize and makemore etch-resistant the surface-modified layer; and subjecting both thestabilized surface-modified layer and a non-modified portion of thesubstrate to dry etching thereby utilizing the higher resistance to saiddry etching of the stabilized surface-modified layer compared to thenon-modified portion, to selectively etch the non-modified portion to adesired depth.
 2. The processing method according to claim 1, whereinthe annealing is conducted by heating by electromagnetic waveirradiation.
 3. The processing method according to claim 2, wherein theheating is conducted by electromagnetic wave irradiation provided by alaser or lamp.
 4. The processing method according to claim 1, furthercomprising a step of subjecting the surface-modified layer to selectiveirradiation with a second light to effect the annealing.
 5. Theprocessing method according to claim 4, wherein the irradiation with thesecond light is conducted using a laser or lamp.
 6. The processingmethod according to claim 1, wherein the surface of the substratecomprises aluminum.
 7. The processing method according to claim 1,wherein the surface of the substrate comprises silicon.
 8. Theprocessing method according to claim 1, wherein the annealing stabilizesthe surface-modified layer by increasing grain size or crystallizationin solid phase.
 9. The processing method according to claim 1, whereinthe surface of the substrate comprises an amorphous silicon filmcontaining hydrogen.
 10. The processing method according to claim 9 inwhich the selective irradiation with light forms a pattern of siliconoxide to provide the surface-modified layer and wherein the annealingremoves hydrogen atoms in the silicon oxide to stabilize thesurface-modified layer.
 11. The processing method according to claim 1,further comprising, prior to the step of subjecting a surface of asubstrate to selective irradiation, a step of:exposing to a low pressureatmosphere comprising a modifying gas comprising oxygen or nitrogen, asubstrate having at least a surface thereof cooled to adsorb themodifying gas onto the surface.
 12. The processing method according toclaim 11, wherein the surface-modified layer is an oxide of thesubstrate and the oxide is formed by oxidation of the substrate.
 13. Theprocessing method according to claim 11, wherein the surface-modifiedlayer is a nitride of the substrate and the nitride is formed byreaction of nitrogen with the substrate.
 14. The processing methodaccording to claim 11, wherein the etching is carried out at an etchingratio such that the surface-modified layer is not etched until apredetermined depth of etching of the non-modified surface portion iscompleted.
 15. The processing method according to claim 11, comprising astep of cleaning the surface of the substrate prior to exposing thesubstrate to the modifying gas.
 16. The processing method according toclaim 11, wherein the surface of the substrate is maintained near thetemperature at which a pressure of the modifying gas reaches a saturatedvapor pressure.
 17. The processing method according to claim 11, whereinthe surface is cooled to a temperature between about 0° C. and about-170° C.
 18. The processing method according to claim 11, wherein theatmosphere comprising oxygen comprises nitrogen oxide.
 19. Theprocessing method according to claim 11, wherein the atmospherecomprising nitrogen comprises ammonia.
 20. The processing methodaccording to claim 11, wherein the substrate comprises silicon atoms atthe surface thereof.
 21. The processing method according to claim 11,wherein the substrate comprises poly Si.
 22. The processing methodaccording to claim 11, wherein the substrate comprises aluminum atoms atthe surface thereof.
 23. The processing method according to claim 11,wherein the substrate comprises aluminum.
 24. The processing methodaccording to claim 1, wherein the annealing is conducted by heatingemploying a heater.
 25. The processing method according to claim 2,wherein the light and the electromagnetic wave are laser lightsdifferent from each other.
 26. The processing method according to claim25, wherein the light is from a KrF laser, and wherein theelectromagnetic wave is from a YAG laser or F₂ laser.
 27. The processingmethod according to claim 2, wherein the electromagnetic wave isselectively absorbed by the surface-modified layer.